...still looking for some reference. Our affected aircraft have a note in the TLB but so far I didn't manage to find an official statement from Airbus.
On the affected aircraft the ATSU date output is immediately scrambled (time show like B1:21 instead of 01:21) as the clock is switched to GPS. Other aircraft can use GPS time just fine.
Also the MSN of the affected aircraft don't seem consecutive, some are older, some brand new.