N-S no drama and by October/ November they should've replaced the bridge that got washed out in the recent floods.
Derby also fine, but Blue Tier in October and early November might still be a bit damp post winter, depending on spring rainfall.
Agreed,
North/South I've ridden in the middle of winter with snow on the upper parts and no issues apart from the logs being a no go zone. It has a lot of rock in the top section and is well built and the lower section has quite a gravely type of surface that rides well wet. But it was seriously messed up from the flood a month back.
Derby is no issue all year round, the rocks have great grip and the soil drains really well, and as rangersac said Blue Tier is the only part that has some issues when it's really wet but it does get hammered by the constant shuttles so it does pretty good really.
Most of the time in Tassie, unless it's pissing with rain you can get out for a ride.