Tivo Cable Cards & Adding HBO

We have two televisions, each connected to a Tivo DVR with cable cards from Xfinity. Both televisions and DVR's work perfectly.

I understand I cannot switch my Xfinity cable plan, or I run the risk of the cable cards no longer working. But if I stick with the same plan I have now, and add HBO as a premium channel, will that cause my cable cards to stop working?