Okay. Let me clarify this for you.
1) Yes you will need to have your DVR (tivo) connected to a phone line at all times. Whoever says differently does not know what they are talking about. Why do I say this? Because at the end of the day, and when you have a problem and call up DTV because you are getting a message on how your DVR hasn't made a daily callback ... I'm the person you will no doubt speak with.
2) You do not need to have your regular receivers connected to a phone line. About DTV charging you full price each month for each receiver? That is not correct. If you want to order ippv (ordering ppv with your remote control) then yes, you will need to have a phone line going into that receiver.
Now there were a few posts mentioning on how you can order ppv and never be billed for it if you don't have the receiver connected..... you can't cheat out DTV forever with those unbilled ppv's.
Can you order ppv (via automated phone line, live represenative, or directv.com) on a receiveer that isn't connected? Of course! You just can't do it over the remote control. Frankly, I think orderling online is the easiest as it will mirror to all of your receivers and there isn't a fee either (automated phone line $1.50).
And why do you ask the DVR needs to be connected to a phone line at all times? It's continually updating the software information, continue loading new guide data and if you leave the DVR unplugged any longer than a few days it will notice this as it typically makes a daily call back... daily. If you don't have it unplugged you will eventually get a message along the lines of
"Your DVR has not made a daily callback in 14 days and it needs to make one" If it doesn't you slowly lose the features of the DVR. I've had customers call in and try to tell me they were told they could have the DVR without connecting it to a phone line. This isn't true. You either have to keep it connected or don't use the DVR.
Hope that answers your questions and any others feel free to ask!