Doesn't having two platforms at BA also have the added problem of needing a new footbridge (disability act etc) as barrow crossings are a no no now?. With the two trains and no signalling, what about a catch point on the Gunnislake branch before the junction that can only be released when the token off the Tavistock train has arrived at BA therefore that train is stopped in the platform and the Gunnislake train is running under caution into the platform to join up?, or another idea, the token section is still St Bx- Gunnislake and the catch point is on the Tavistock branch coming into BA with the second token BA-TK.
The reason I thought of the first idea is if the TK over runs it would 'harmlessly' back down to Ply, and If the Gunnislake does so, its in the dirt (or over run in the former Up platform area) and cannot contact the TK train.
Antony