Couple of weekends back when there was a block between Wolverhampton and Penkridge, XC Manchester services went via a reversal at Nuneaton. So it would seem that no, it's not signed by them. (I forget what VT did.)
At the weekend the Cannock line passenger services are half-hourly, with several FLHH services to and from Rugeley Power station. This may not sound much but the line is still at present signalled Absolute Block. This does mean that capacity is limited. There are only three signalboxes on the route as many were closed in the BR era.
The imminent resignalling project will increase capacity on this line.