Correct level to attain is 46. I know this because I am in PoFire with my 46 ranger fully EP flagged waiting on the EP gods to spawn to get it a full and legit Time flag. Also while a lot of the gear is not usable till level 65, the push rule applies. A level 46 can zone into all Planes of Power zones either through proper flagging or by the pushing rule. So all PoP gear needs a proper fix to change nearly any/all gear/items level to attain 46.
The exception being, Bor Warhammers line of gear. They may in fact be required level 55 to attain, if I get time flagged before than I will update.
Just thought I would throw in my 2 SP.