I figured I'd give it a bit to see if anyone else wanted to jump in but, since things seem pretty silent around here, this is what I can tell you, as "someone in the know".
This lineage is not "defunct". I can confirm at least one new Probationer within the past two years (there may be more, but I'm only personally aware of the one).
That individual (K, for convenience) was in a similar situation to yourself and myself -- feeling an inexplicable drawing toward this particular lineage. K reached out via email and snail mail a few times with no response and ultimately, living in Los Angeles, ended up going to one of the Temple of Thelema public classes to talk with someone in person. At that class, K was told that the College of Thelema was, for all intents and purposes, defunct, and that Temple of Thelema was the necessary "on-ramp" for the A.'.A.'..
It was about two years into K's Temple of Thelema experience that K told me this history and further told me that s/he probably had at least another 2-3 years (or more) to go before being qualified to become a Probationer (this was about two and a half years ago). That projected timeline pretty much broke my own inexplicable drawing to this lineage and it was around that time that I wrote to the email address I gave previously and received an almost immediate reply to begin the traditional 3 month Student Grade.
I've since learned that my experience motivated K to pull some strings, push some levers -- do some Magick, I suppose -- and get admitted as a Probationer much sooner than typical, but still it was at least a two and a half year process.
That was my recalibration process, FWIW.