Can the X-Link be used for control?

Yes it can . Control operations generally require a certain speed threshold, deterministic operation, and reliable data transport. X-Link has the inherent speed necessary for all but the most demanding control operations and supports a number of deterministic protocols (A-B Remote I/O, Profibus DP, Reliance Rail I/O, Modicon Remote I/O, etc…) specifically designed for control-type applications.