Bell TV does not even officially support DP/DPP equipment, even though it works just fine. It will be interesting if they do infact use half of the TPs on Nimiq5 @ 72.7W. Knowing them they will probably offer SW64 swiches instead of DPP44 switches lol.
Bell were supplying SW64's to installers a while ago when they ran out of SW44's, so I think you will be correct, Bell will stay with Legacy switch's, when 72.7 comes on line.
I know they do support DishPro and the dual tuner ones most definitely support DishProPlus. Scott (site owner) has a DPPTwin on his dual tuner HD unit with the separator
I have a 9242 and I use a DPP Twin with the separator on mine also. Works perfectly. I bought my DPP from dishstore.net, which is Scott's site. Great service.
As far as I know there is no problem using DP or DPP, the only thing is that as Bell do not "officially" support DP & DPP, if you call in for any kind of problem, DO NOT tell them you are using it, you will confuse the CSR's who will have no idea what they are.