Went onto Facebook Messenger and chatted to get an answer. For the benefit of others, here is the answer from Stephanie C. "...what I'm seeing is that at least one of the phones needed to be used on a line, but nothing specific about all of the phones needing to be used on all of the lines."
With this, I have no reason to believe there will be an issue with my rebate.
Glad to here you got a reply from our T-Force folks. Did you have any other questions about this promo?