The Activators were originally envisioned as replacements for the OEM pickups, so I'd guess they would interchange . . . . but as always, you'll need somemeasurements or have them in hand to match 'em up. And too, the PJ Activators use that spring height adjustment, so I don't know if you could go the wood-screw route a lot of Fenders use, or if the springs would work on the EMG's. Anyhow, I doubt there's major surgery involved.
I had a bass with PJ EMG's once (using their BTC network, all 'plug and play') and I did admire how deathly quiet they were. And EMG's to me seem 'voiced': It didn't take much to get a great tone fast, nowhere near the range of a typical Alembic setup, which can be good or bad, depending on the player. They were in an Ash-bodied, all maple neck Fernandes, and they quite easily got pretty fat without incorporating as much 'squawk' as you'd expect out of that wood recipe.
Go for it. It's your bass and your taste, lots of guitars have different pickups.
J o e y
