Some other interesting information about E-15. First, it appears to be exactly like E-11 in that it can provide all 32 TPs at a DBS slot in double power mode or 19 TPs in triple power mode. I assume this was done to speed up the build up of E-15 since the design would require few changes but it does leave somewhat of a problem for Dish. E-12 can provide 13 TPs at 61.5 W but only 12 in spotbeam mode. So if Dish wants to use E-15 fully in triple power mode than either E-12 is going to have to pick up some CONUS slack or E-3 is going to have to provide it. Otherwise a few CONUS TPs from E-15 will have to be provided in only double power mode. Dish could also just not use a single TP at 61.5 W. We may get some clues from the downlink report during the testing of E-15.
Indeed, that was one of the more interesting pieces of the launch broadcast, that it was essentially a rebuild of E11. E15 was ordered just a few weeks after AMC-14 was determined to be a loss, so I guess that is what sped up the design. I also believe it has an antenna for use in the Western Arc so in the future it can serve there easily. Wouldn't be surprised if it was essentially the E11 footprint there. I do wonder if E16 will have some CONUS capacity that might enable triple power on all E15 TPs while not wasting space.
Since Dish does only have STA on TP 23, I guess they could leave it empty, or as has been said, leaving some on only double power QPSK. Some people do need them, as 61.5 still carries some internationals, and some people that get them still probably have legacy equipment. But having E12 carry a CONUS TP in lieu expanding HD LiL would be more of a mistake than just letting a TP go empty.