Not really. I've opened about a dozen of them this way and changed the lighting to LED lighting, never had any issues with breakage. They're actually pretty flexible. The sides of the car do bow out some as you are taking the top off, but they are not damaged in any way. Just don't get carried away, it's only necessary to release all of the catches at once and then slide the top off.
I can tell you that it's impossible to open them using Lionel's instructions! I fooled with them for the better part of half an hour when I tried opening the first one, finally decided to work out an alternate method of opening them.
