My guess is: Probably.
I use Mandrake 9.0, 9.1, and 9.2 RPMs on Mandrake 10.0 and don't usually have problems. Of course, I prefer to use MDK 10.0 rpms, but the reality is that the file system, config, and general set up of the distro between thouse 4 releases hasn't altered all that much. The only time you're likely to run into problems is when you're trying to use an RPM from a different distro -- usually then the way the disrto is put together varies such that you have all sorts of dependancy issues.
Likely the majority of Fedora Core 1 RPMS will work fine, with the exception of a few.
Please tell me if I'm wrong, Fedore Core 2 Test 2 users!