I assume it's being done by Sierra, it was Sierra's staff who were plugging the game at
Play.com Live at Wembley.
There aren't that many Ectos that'd really cut the grade in terms of promoting the game… but rest assured, Sierra's UK arm has also got access to a Ecto-1 replica which it has used for one promo event and mght use it for more.
As for getting hired onto promotions going around the country, I'd suggest instead of that if people wished to help promot the game, that they atten the conventions in costume, maybe with flyers advertising the game. Some people in the States have also been talking about appearing at games stores in costume to help the promotion on the day/night of release, however I'd strongly suggest consulting the games store manager close to the release date to see if they'd be interested and willing to do it. It'd be better to be safe and prepared then to turn up on the night and possibly have an argument with the staff.