How would you remove the "lock"

Looks like you'd use an Allen key.

Yep, you use an Allen key, these are a nice design but are a pain to service I would imagine. Whenever I got this the top wouldn't "twist" off, so I had to remove all eight screws and nuts on the top between the top reflector and refractor and loosen the screws inside.

Allen key? Is it one of these:

Yes.

I think I see why they are replacing all the twist-paks with Cobraheads, cause these things are a pain to service. xD

But aren't all post tops harder to service than cobraheads?

Nope, the main reason is that the underground wiring is close to 50 years old and much of it has begun to fail. Also the fact that the lights don't meet current standards. The fact that the lights are harder to service is only a very minor reason for the " upgrades."