This is a funny subject given my lengthy experiences with SKY who have to say are thick as 2 shites, know more about the poxy sky boxes than the engineers installing or doing service calls, you know I had to show the guy what sky + was while he was servicing my systems for faults developed because of there ***** system upgrades, fecking useless, anyway back on cue.
The line connection is compulsory for the all boxes in a multi room connection before & after the initial contract length, small print, but as already advised single boxes arent an issue mostly unless you're in the 1st 12 months of the contract, after that you can argue the contract is up & I dont want it connected anymore, but think small print says must be connected at all times whilst subscribing to sky on all customers but they never used to mind single boxes being unconnected.
The boxes dial up different times of month, so might get caught this way & as advised if they dont see a monthly callback you'll get crappy letters which I did even when the poxy thing was connected & I did forced callbacks with the bangalore/outer mongolia call centers on my cellphone, so make of that what you will, but what you can do is once a month do a force callback through select 01 menus & then it will register the callback with them, but ideally from the original location not from the other house.
But to add my number on the account is my cell, not home & it still calls back from the house with number witheld & shows as callbacks so does make you wonder if sticking withheld in the dial string in menus will work for your scenario aswell cause they dont get network cli (calling line identity passed by telecom network to telecom network exclusively) just the normal cli we use & block from our locations, so worth a go, as long as they see callback & from right sky card/box then might be ok.
But note sky card is paired with box so wont work in another box unless re-paired wth that box & of course valid reason for that needs to be given.
There are other ways round these things if you had 2 phone lines at parents house with multiple line smart box from say Mitel namely the Smart1, but comes down to economics at end of day.
With widespread use of adsl & no doubt every home will have it, in future the boxes will be net connected so this will be obsolete anyway for dialling up & sky will have a serious competition on there hands if the networks are fast enough to stream to so many people & other countries allow us to subcribe to them, at present there's country blocks which is annoying unless you have a proxy in that country.
I HATE SKY but in our area there's no one else & channels 1-5 are just plain crap, so for peace of mind for my brother not whingeing in ear hole, we use.
New epg is purely for hd box users but cause of many bugs the rollout was delayed given thomson boxes were 1st with all boxes then they slowly ironed out bugs & released to other hd box makers units like samsung etc, rollout for samsung seems to be last as still havnt got mine yet, force upgrade to see if its available for your box yet, by removing power, hold down Backup button, plug power in whilst still holding Backup button until tv shows upgrade in progress & front panel on hd box lights up like xmas tree & phone line must be connected for upgrades.
Been many reports of bugs even now on latest incarnation, so you've been warned.