First thing you do when shooting tapeles...ANY form of tapeless...is back up the FULL card. Not some small folder that have the video files, the full card. So please tell me the full card was backed up. Without the full card...using this footage with ANY NLE will be tricky.
Once you do that... well, am I right in assuming this is XDCAM-EX footage? I think that's the only format with BPAV. OK, if you have the full card, then you need to download the Sony XDCAM Transfer Utility and use that...or the XDCAM log and transfer utility and use that:
Sorry...no. FCP 5 cannot work with this format at all. That format was introduced years after FCP 5 was released. FCP 5 doesn't do XDCAM. It doesn't do ProRes. So you cannot convert that footage on that machine to work with your version of FCP.
Well, I don't know about that really, not sure if it will work on that machine. You can try the XDCAM Transfer Utility to convert the footage...well, wrap the footage to a QT file. But then you'd need to convert it to a format FCP 5 works with. And your choices are limited. Uncompressed HD will keep the full raster dimensions of it, but that requires a very fast RAID to play back (firewire won't cut it). Or you can convert to DVCPRO HD...but that will cause a bit of quality loss as you go from full raster 1920x100 to ultra thin raster 1280x1080.
IF you can get it to work. That's a very outdated editing system...and a pretty current camera format. They might not mesh at all.