From Apple's web site:
"FireWire device control for streaming capture for tape-based HDV, DV, DVCAM, DVCPRO, DVCPRO 50, and DVCPRO HD."
There is no list of supported cameras, that statement is it, that's all Apple will tell you about video tape and Final Cut Pro. You may want to try QuickTime Player for capturing from video tape, also. It often works better.
Now, very few cameras record to video tape anymore, so that's a dead technology at this point. But if you get a Firwire to USB adapter, you should be able to capture from the DVX 100a. It'll cut the recording up by timecode breaks, which are frequent on video camera tapes, just the nature of tape that stretches.
You'll have to try it and see. Some folks have moderate success, but I'd super highly recommend getting off of video tape for a huge number of reasons.