Didn't the Enterprise-E already left Romulan space by the time it reached the Bassed rift and crossed into the Neutral Zone?
The last we hear is that they are "headed for Federation space"; earlier on, Shinzon boasted that they'd never make it out of the RNZ.
Just before the fight, less than a minute before they enter Bassen, Data says that the fleet is about 40 minutes away. This, then, is the likely location of the border, too.
They also informed Starfleet of what Shinzon wanted to do via subspace, hence why the taskforce was assembled and waiting. Its likely the rift sits in the Neutral Zone bordering with Federation space.
Possibly so. But the only reason for the fleet to stop, rather than to meet with the E-E, would be if they were not allowed to cross the border. The threat from Shinzon could be countered at two locations only: Earth, and the current location of the E-E. Waiting would serve no purpose if alternatives existed.
And yes, while I understand the dance both Romulans and the Federation played bordering with the Neutral Zone in TNG... neither ship from either side was allowed to cross into the N.Z. without explicit permission on both sides.
Yet both did, just as in TOS, and there never was war. So the risk probably wasn't deemed all that high whenever a skipper pondered whether to violate the treaty or not. But at this particular time, erring to the side of caution (and Federation) might have been a pretty good idea, especially as Picard had been able to tell Starfleet all about this enemy who apparently was at odds with the rest of Romulus.
Shinzon technically violated that agreement and he crossed into the N.Z while in pursuit of the Enterprise... also, since the rift disrupts all subspace communications, the fleet might have gone inside the rift without being detected... however, long range sensors might have seen the fleet entering the rift in that case (unless SF had a clever way to fool the Romulan sensors and make them think the fleet was still waiting).
...Perhaps the fleet
was inside the rift, but due to its sensor-fouling properties, never managed to locate the fight?
But the writers didn't quite understand what they were writing here: it made no tactical sense for Shinzon to wait until Bassen before making his move. The comms blackout did not provide any advantage, and in any case, Shinzon deliberately squandered any extra minutes he might have gained.
Then again, little or nothing that Shinzon did made any sense, and squandering was one of his superpowers...
Vance is a bigger mystery here, while Osyraa might have something up her sleeve as well, instead of being all cardboard. But the plots themselves don't suffer if it turns out there's no mystery or depth to these characters. Unlike in ST:NEM.
Timo Saloniemi