I would think the 861v8 (possibly v6/v4/G6*, I forget it's limits) would know that and add appropriate delay.
One the 861 the lip-sync delay is 0mS to 50mS, though there is a trade off when the number of MRC filters exceeds are certain value.
All the lip-sync delays all channels by the same amount. However I agree with you that it is plausible for the 861 to compensate for the EBA latency.
I guess eventually M will rollout EBA to all (well current range at least) DSP's.
Today all DSP's have a unified latency of 7.5mS so a 40ms with EBA is quite a jump and problematical for movies.
Regards,
Carl
IIRC early video processor added quite a large delay to the video stream, which gave rise to lip sync problems but I don't know if this is still the case.