Josh, I could confirm that phone line are used to track receivers...
I used to work for the SAT team, the departement that "verifies" receiver and assures that Bell's cottage policy is followed.
When your receiver is not "dialling out" Bell Express Vu after a X number of failed attempts to get the info from your receiver will put you on a "to call" list.
Since there is lots of suscribers and Bell TV doesn't have a huge budget to have a large team on this that team mainly focus on those that have 3 receivers or more, since they are the ones that are the most likely to have receivers in 2 locations.
Your friend is probably on that "to call" list. Depending on how many agents are at the time working in that departement, depending on how many receivers he has listed in his account, if he vere, or the friend he gave the receiver to, mentionned that receiver where not in the same location, will soon a later get a call to get his receivers "verified". Also, if the friend he gaved the receiver to has his phone line connected, but your friend doesn't Bell doesn't get the info on both locations.