In reply to Mr Fuller:
I had ligament reconstruction surgery in both thumbs (one skiing, one football) around 8-9 years ago. I wasn't into climbing at the time so can't answer how long it would take to start climbing but I seem to remember something around 6 weeks to start using it.
I could be wrong though, it's so long ago I can't remember - I do remember being weaker for a while (eg unscrewing bottles) but not sure if it was loss of strength or the fact that I was a bit sore. I do vividly remember that I felt a bit unsure of opening it/extending it too much at first - I remember not wrapping my thumb around a ping glass at first and holding it with 4 fingers.
I got into climbing a few years later, I thought it would be a handicap as I was left with the mental impression of having weak thumbs but can't say it was a problem. Hurts a bit when holding on for dear life and overdoing it but probably would have hurt anyway.
I am no doctor but I would have thought that you'll need a few months before being able to climb and then a few months to build strength up - winter sounds a bit tight, especially for climbing really hard at the level you used to. I'd guess that in winter you'll be on your way of building strength back up. Obviously your doctor should be able to advise further but don't forget that these guys don't always understand what climbing involves.
I know it sucks but it's worth taking the time to rehabilitate it properly and gradually build up strength etc to minimise the chances of problems. If I were you I'd start strength exercises as soon as the doctor gives you the ok to do so (start slow and nothing that risks damaging it obviously) and regarding climbing, I'd probably do some super easy climbing at a wall for a bit.
I do seem to remember my doctor saying that I can do 'everything' as soon as the bandages/stitches came off so your doctor might say the same but it sounds to me that going straight back to hard routes after loss of strength is not the best idea. I never fully understood what the reconstruction exactly does and whether you can actually 'strengthen' the structure they put in place - worth asking to understand...