I get a special "corporate" discount for my AT&T services (being military has a few benefits). So far, I have not seen ANY discounts that would allow me to cite the fact that I have AT&T landline phone, AT&T DSL and AT&T wireless. Considering that I have THREE cell lines on my account, I could use a discount or two right now.
I noted a couple of weeks ago that AT&T is now seriously looking at a contract with DirecTV as soon as their current DishNetwork contract expires. Guess which satellite service I use... Yep, DirecTV. Hopefully, I'll be able to get some sort of "quadfecta" discount at that time...