However, ST:NEM then indicates that the particular region of the RNZ shown in the "BoT" map remains unaltered in a late 24th century floor mosaic, for the relevant part. That is, the thickness of the RNZ relative to the dot-to-dot distances on the original map has not changed. All respect to preservation of ancient art and whatnot - but would it be plausible that the Romulan Senate would continue to feature artwork depicting a political situation that is significantly less advantageous to Romulus than the true, current one?
The other thing to consider is "The Enterprise Incident". If we're talking about the BOT Map as being of inside a star system and it only being several AU across (because of the comet) then when the Enterprise scans out across a whole Parsec (and found nothing) it should've picked up Romulus/Romii as well.