The high speed rail line seems to terminate at Shenzhen North Station. By 2015, the line will be extended to West Kowloon, Hong Kong. But now, high speed rail line between Guangzhou East and Shenzhen has still been operated. And, From Shenzhen to Honghum in Hong Kong, East Rail Line has already played a role in connecting Mainland China and Hong Kong. So, high speed trains can run on the line, but the case is not so.
It can be because Hong Kong MTR doesn't trust safety of high speed trains in Mainland China.
Similar to that, construction of Shenzhen North-Kowloon West Line was protested by some Hong Kongers.
I'd like to see how residents in HK behave after completion of the line.