When I installed mine I think it said it would only work with the disk I had in the machine at the time (disk number yadda yadda). I don't think I had the disk actually in the machine because I left it out not for the game to start and to go into the store or whatever I had to do (was a while ago).
I was wondering something similar because my PS3 wasn't working at the time and wouldn't actually let me play COD4 after installing the maps (people who read posts regularly on here might remember I couldn't play COD3 either and made a discussion on it, I bought COD4 and that wouldn't work either!).
I was wondering if I had to send the PS3 back would I be able to reinstall the maps if they replaced my console. My PS3 is sorted now, but would still like to know, but I think it is linked to the disk it came with (I didn't think they could do that though?) so you should be able to I think...
Do you know someone else with a PS3 that can try it?