How would cbtc help anything?
Do you know what CBTC is? It's a technology that would allow trains to be closee to another but still maintain safe distances, much better than the current block system allows. This ultimately leads to more TPH.
But as Stephen Bauman pointed out (cryptically, I must admit), there are also management issues that need to be addressed to get more than 28 tph. Trains have to be timed very precisely; otherwise you won't get proper throughput at terminals and merges.
So, better management with current signaling could probably allow more trains than currently. Better signaling without better management probably wouldn't allow any improvement. Better management AND better signaling probably would allow even more trains.