I don't think so...
As far as I know, those car remotes all use radio signals, which won't be transmitted by the phone.
Even if some of them use acoustic signals, the phone system only passes frequencies in the audible range. Try this: hold the remote up to your ear and press the button. Hear the tones? No? Then whatever signal the remote is emitting isn't something that will travel by telephone.
On the other hand, I suppose it would be amusing to watch people try the car-remote-over-the-phone trick.

Call me a skeptic. You'll have to show me, or at least tell me you've done this yourself.

Just tried it. Dosen't work with my AT&T. Can you hear me now?

Snopes has already debunked this... http://www.snopes.com/autos/techno/keyless.asp