CR
While the sat tracking system is internet fed, it's not the only means there is of tracking the aircraft.
They are also fitted with AIS, which does not give as much info, but has a faster update speed on position.
Even then the decision has been made to keep regular VHF "ops normals" with the aircraft as well.
ARCC does use the sat tracking system as far as I know. Certainly I've heard of them chasing the MRCC for an update because they've noticed the aircraft's up before the MRCC have had a chance to call them.