Not only that, but we also know that there appear to be two/three distinct versions of the car, quite something when recalled that Ghostbusters (1984) and Ghostbusters II had three cars between them.
Upping the car count is the intriguing decision to have two variants of the same car, one evidently a slight upgrade over the other, on location, rather than upgrade a single car... At a guess this is probably a move to reduce the amount of time needed to film in Boston.
A further intriguing element is a forth car, a similar vintage Cadillac (a sedan rather than a hearse), painted black with only the large amber rotator and the LED lightbar. There's speculation, bolstered by the presence of a beefy bumper, that this is a stunt vehicle. Given it's got the lights attached to the exterior, I'd wager this is for filming internal shots only, whilst having the car's lighting effects.
Make: Either a 1983 Cadillac Superior Hearse or a 1984 Cadillac Fleetwood Hearse.
Car #1 - The "Primer"
Specifically speaking, there isn't actually any obvious primer on this version of the car, however... Given the convention of the 1984 film... I feel this is a good way of identifying this car against the other two. In its unmodified form, the "Primer" has black bodywork with a red roof and a stock Cadillac hood ornament. This is the car before it becomes what will be the film's version of Ecto-1. [As of this writing, I could not confirm if the car sports the yellow rotating beacon seen on the other versions]
Car #2 - The "Ecto-1"
The black bodywork has been traded for white, with red striping along the side (reminiscent of a discarded colour scheme design by Steve Dane).
The logos on the car are a modification of the classic logo, featuring a slight tweaking of the ghost's and thinning of the red circle and crossbar. Topping the car off is a large yellow rotating beacon (inspired by similar makes of Hearse which were fitted with such a feature), a predominantly white roof rack with yellow and black hazard tape.
The roof rack includes a blue and white bullhorn, a black reel with a red hose or cable, a grey box with hazard tape detailing with vents on the side, a second box with small aerials and a prominent warning label, a large silver tank with a radioactive label (which attaches to the tank with the aerials via a tube). Attached near the rear of the vehicle is a swimming pool ladder.
Car #3 - The "Ecto-1A"
This vehicle is largely identical to the other hero vehicle, the main difference is that the box with warning label has been replaced by a second tank, and a red/blue LED lightbar has been included on the rear of the vehicle.
Note: After studying photographs of the various cars, aside from the roof rack there is also a subtle tell as to which of the red & white cars is the "E1" vehicle and which is the "E1A", the "E1" vehicle's orange indicator lights cover the front and sides of the car, the "E1A" vehicle's orange indicators are present only on the side, and are clear on the front.
It's also possible to see where the Cadillac details have been removed from the "before" vehicle's indicators.
Driver-side door logo
The hood ornament detail (Note: The ornament has been designed to rotate in order to allow the car's hood to open)
The Ecto-1's licence plate.
There isn't much reference of the interior of the cars yet, although thanks to the recent block of filming in New York, we're starting to get a bit of an idea. It would appear (as depicted in the photo below) that unlike the cars in the 1984 and 1989 movies, the 2016 Proton Packs are stowed in a "two by two" configuration, rather than four in a line. However it would appear that like the previous movies, the Packs are removed from the 2016 Ecto-1 on a sliding apparatus.
The Roof Rack
Also thanks to the recent filming in New York, we're not starting to see some great reference material for the roof equipment. As of this writing the best of reference is only of the "E1" car, however it's possible we may see some material of the "E1A" car as time progresses (both cars are in New York, and both appear to be filming different segments around the city).
The most easily-to-identify elements (on both cars) are as follows:
∙A large custom amber rotating beacon - inspired by features found on some hearse models of the era the cars were manufactured.
∙A blue and white bullhorn with microphone and carry strap (strap, handle and logo panel removed) - So far the Hamilton Buhl MM-9 Mighty Megaphone looks to be an extremely good match for the bullhorn on the car. It should be noted (as depicted in the photos) that the bullhorn is attached to the front, hashed bar of the car's roof rack
∙A black hose reel with a red hose - This would appear to be a black plastic hose reel which may've once held an electrical cable. The original cable has been replaced by what appears to be a red pneumatic air hose.
∙A large silver gas cylinder with a prominent central dividing line - the cylinder has been painted silver, and appears to have been fitted with some detail gauges near to what would have been the top. A radiation stick has been added to the base, and a warning "WARNING - PARTS MAY FALL OFF" has been applied to the side of the cylinder. A connection pipe with a wheel valve has been added, connecting it to another element of the roof rack.
∙A red/blue LED lightbar (Only present on the E1A car) is fitted on the back of the Ecto-1 - The red LEDs are located on the driver side, the blue on the passenger side.
This post is currently subject to revision as new information comes in.