In theory, the "new" pad is to honour Grimnar's ascension to Great Wolf so existing members of his Company at the time should be chuffed to bits that they get to wear it, that their Wolf Lord made it to the top spot. However - this being the Wolves - there's bound to be a couple of stubborn buggers that held onto the old one, and again being the Wolves, they've probably let them keep it.
Kevin is also correct in that his Wolf Guard are still part of Grimnar's Great Company. Like any other Wolf Lord, he picks them out from his own company - though apparently, as Arjac shows, as Great Wolf he gets to nick them from elsewhere too...