The question seemed to me to be about the new Digital One slots, not a new Digital One transmitter site, it has been asked on Digital Spy, as the Digital One website gives no indication as to what these slots are for, the thread is here but at the moment it's just speculation.

http://www.digitalspy.co.uk/forums/showthread.php?t=873969

Ofcom have allowed Channel 4 to delay the launch date of their second national multiplex. IIRC they have to give Ofcom their revised plans by the end of this month. They have been in discussions with Global about an interim solution of using spare capacity on Digital One. They've also recently been advertising several E4 Radio staff positions.