I believe the code for selecting live vs test was removed years ago, but the command line switch was never removed. So as far as I know, that switch does nothing.

I have used SEQ with the test server, but it requires the opcodes and structs for the test server, which are different than live, and also change pretty much every patch to test.

I used to post patches for test when I was regularly playing there. But I haven't kept up with it as I haven't had much time to play lately.

As BA said - if you know how to find the offsets/structs for live, then the same techniques can be applied to test.