Well the new rubbish depot and recycling plant at Millerhill is fairly complete, a facility to be shared by Edinburgh, East and Mid Lothian I believe. When that's up and running I believe the Powderhall Compactor can close, at least for the purposes of being a rubbish sorting and rail dispatch depot. Council might of course keep it on for other reasons but assume they'd be falling over themselves to sell it for flats.
I would assume that any Powderhall to Lochend path could provide access at;
St. Marks's Park, Broughton Road (or Blandfield), Dryden Terrace, Leith Walk, Easter Road, "Urbane Den".
Realistically any access to Leith Walk and/or Easter Road might not be direct to those roads, it might be in the nearest conveinient side street. e.g. Shrub Place lane for Leith Walk, Harrismith Place or Sunnyside for Easter Road.