As far as I'm aware, the arms stay with the name. If the then chief of Clan Maciver renounced his name, he would also have to renounce the arms associated with that name, which could then be applied for by whoever succeeded the chap who changed his name. None of the Campbells would have been able to use those arms without changing their name also.
Looking in Burke's General Armory, it shows two entries for McIver - the first is in the surname of M'Iver and is given as Quarterly Or and Gules a Bend Sable.
The second is in the surname of M'Iver Campbell and the arms have the undifferenced Campbell arms in the 1st quarter and include the first M'Iver arms in the 4th quarter. The Crest and Motto are the same for both. So it would appear that the Chief didn't renounce his M'Iver name at all, just changed it to M'Iver Campbell and inherited another three quarterings for his shield. I would imagine that to find out all the legalities involved you would have to enquire of the Office of the Lord Lyon as he is the arbiter of all heraldic things Scottish.