It's pretty much all hills, all the time, for me...although the big 1 hourish climbs are all snowed in for me, so most of my winter climbing is a series of <20 minute hills strung together. Even those often have ice/moisture and sand on them...it's virtually impossible for me to not do a climb-heavy route without driving somewhere.
One difference from summer, is I do a lot of zone 2 rides on the trainer. Zone 2 is hard to stick to on local roads and everything from my aerobic base to threshold and repeatability of efforts, has improved since working on that. The other thing I work heavily on in the winter, is strength training. It's not just for better all-around fitness, but to also improve endurance on the bike.
There is a mental aspect of climbing that is hard to replicate outside of just doing it, but it mostly comes down to watts per kg. So simply, I just try to build my FTP and avoid putting on weight.