From Terms and Conditions
4. Right to Transfer a Subscription: Satellite Radio Service Subscriptions (other than lifetime Subscriptions) are transferable from one Receiver to another. A LIFETIME SATELLITE RADIO SUBSCRIPTION (WHICH IS A SUBSCRIPTION THAT CONTINUES FOR THE LIFE OF THE RECEIVER) IS NOT TRANSFERABLE IF IT IS ASSOCIATED WITH A RECEIVER INSTALLED BY AN AUTOMAKER OR AN AUTOMOTIVE DEALER IN A VEHICLE, EXCEPT IN THE EVENT THE ORIGINAL RECEIVER ASSOCIATED WITH THAT LIFETIME SATELLITE RADIO SUBSCRIPTION IS STOLEN, ACCIDENTALLY DAMAGED OR, IN OUR SOLE DISCRETION, IS DEFECTIVE. A LIFETIME SATELLITE RADIO SUBSCRIPTION ASSOCIATED WITH A HOME, PORTABLE OR PLUG & PLAY RECEIVER IS TRANSFERABLE FROM ONE RECEIVER TO ANOTHER RECEIVER, UP TO A MAXIMUM OF THREE TIMES. Permitted transfers of Satellite Radio Service Subscriptions are subject to a transfer fee, as set forth herein.
The Billing dept says that if the dealer paid for the lifetime subscription, i.e., BMW, then it cannot be transferred. But if I paid for the subscription, as I did for two units, then I can transfer up to three times. The donkeys that answer the phone to sign up or activate do not know this, as my father just tried to sign up for a lifetime today because the factory sub expires soon. He was persuaded not to do a lifetime because the girl told him that it cannot be transferred. I have spoken to three people at Sirius on the matter and 2 out of 3 say it can be done.
EDIT: After further debate, I have decided to switch to a 1 year plan because of the above link that says they'll charge you $75 to switch. I am able to do this because I have not made a payment yet.