If there is snow but not too much you can borrow snowshoes at bourg st pierre i believe and then send them back via the bus that goes. See
@timr for a lot of info on walking the pass. We went over mid june when it had just opened, still snow on some bits of path which we traversed safely in boots, using poles, but walked final part on the road as too much snow right at the top. The bits we walked across were dodgy , if we had slipped we would have gone some way down. I guess the same applies in september. Not sure if fresh snow more dangerous than melting snow. Best advice is to contact the hospice as gerald carey suggests above.