Under the blended plan, Caltrain and high-speed rail are supposed to share tracks and infrastructure. And yet, for completely inexplicable reasons, Caltrain is installing a PTC signal system incompatible with HSR.
The Caltrain PTC system is called CBOSS. It has already cost the agency over $230 million, a price far higher than comparable PTC projects elsewhere. One reason for the huge cost is that Caltrain elected to develop a custom, in-house system — and this is the inevitable result:
Systemic Failure 
Please help me find the costs of “comparable PTC projects elsewhere?”
Click to access ERTMS_Factsheet_19_ERTMS_deployment_in_Denmark.pdf
http://caltrain-hsr.blogspot.com/2011/10/meanwhile-in-rio.html
http://caltrain-hsr.blogspot.com/2011/08/cboss-vs-metrolink-ptc.html