All flats can currently receive sky HD. There may be some where the signal strength is a little low and it may effect quality. The upgrade is to ensure quality is high enough through out the development. The second stage of the upgrade is to increase the capacity to each stairwell to allow a dual feed. At the moment the ability to view one channel and record another is dependant on the channels in question. Dual feed will mean there is no limit to the channels that may be viewed while another is recorded.
All Sky subscriptions need to be sorted out directly with Sky, who will then provide the equipment, as far as I am aware.
Please do ask away if you have any other questions.
All the best