Hi,
if you have silence safely before or after the recording, you can record white noise to the ADAT Tape with autorecord (Locator 2 and 3 If I remember correct???) at a specific time for a short period. For example if you set in and out to 00:01:00:00-00:01:00:01 on every tape, you can align the resulting noiseburst of every Tape recorded “somewhere” on the timeline.
You might want to set autofade to the lowest possible value (I don’t know if there is “off” available), as the ADAT will do a crossfade when punching in and out, that might make it a bit more difficult to pinpoint the actual in point in the recording.
Hope this helps,
Cheers,
Dirk