VOiP phones when moving house

[raybarrow]

Hi Folks,
House is going up for sale beginning Jan. Virgin are scheduled to change our landline to VOIP on the 9th Jan, although I heard on the news this morning that there's a 'hold' being put on VOIP because of Medic Alerts etc that work on a conventional landline, so who knows.
Anyway when we move we will cancel the Virging contract and return their equipment - router, TIVO box.
Am I write in thinking that anyone who moves into a previously 'VOIP enabled' property, will not have a landline until they sign up for internet/broadband?
Can you have VOIP if you use a mobile router?
This is a curiosity question as where we are going none of that is not a problem.
Cheers,
Ray.