This is a very grey area that has come up before.
I seem to recall that ICAO was going to change the wording in their book and I'm not sure exactly what it says at the moment but the simple rule used to be - when pilot is under own navigation, the pilot is responsible for terrain clearance, in other situations it's ATC. As far as I recall the book said nothing about what service the aircraft was receiving from ATC.
So the grey area was if ATC cleared an aircraft to route own navigation from A to B but is still watching on radar and could just as easily have put the aircraft on a heading to the same place - who is responsible?
This has been the cause of some deep philosophical debates amongst myself and colleagues over the years - with roughly equal numbers on each side of the fence.
I hope that the ICAO rules are now clearer - I guess it will be in PANS-ATM. I'll try to have a look next time I get a chance and give an update if necessary.