I climbed Tikaboo on 12/18/08, the day after the big Vegas snowstorm. With a 4Runner 4WD, I made it to the same spot as in a Highlander 2WD in summer, above the left turn that heads uphill, but below the little detour around the downed tree. There were a couple of iffy rutted zigzags and bumps not long before the left turn, but it powered through them fine in 4WD Low with the center diff locked, without any wheel slip that I noticed.
I think the road was in better shape in 12/08 than in 12/07 when I got stopped by a wash about 2 miles short of the goal in a midsize front drive sedan. I think I would have made it past that point with the sedan in 2008 and gotten stopped much closer to the spring. Then again, maybe the conditions were similar and the 4Runner just made everything look so easy.
I made a continuous 75 minute video of the drive back out from my little parking spot to 93, with my point/shoot camera clamped to the handhold by the top left of the windshield. It shows the place where I'd stopped and backed up a bit on the way in, and walked ahead to decide whether to chicken out and hike from there, or go for it. It also shows how the truck rocked and rolled through the bumps, a few really good ones. Both driving in and leaving, the cattle gate was open, the only times I've seen it that way.
It was 13 degrees out both when I started and when driving out. It was so totally windless and sunny that I had to take my jacket off the whole time hiking, including just standing around on the peak when I thought for sure I'd have to put it back on.
For me, the shale section was actually much easier to climb in snow than dry. It helped me keep my feet level on every step, and slightly acted as grout holding the rocks together. I didn't bring crampons or an ice axe, so I'm glad it was nice packable snow and not sheer ice. Certain types of icy conditions might be OK to climb in there, if it causes more "gluing together of the shale" than it causes danger of slipping.
In summer, on the steepest 10 vertical feet or so I slid downhill slightly or made little forward progress on at least 5 attempted steps upward. In the snow, I didn't slide back once, and didn't even know I'd passed the steepest until it was obviously well behind me. Route finding coming down was extremely easy, just retracing my steps in the snow. One photo I took shows the exact path of my footprints through the whole saddle area, which I'll make a diagram from sometime.
The disadvantage of climbing it in the snow was that more physical effort was required, just as walking in beach sand takes more effort. Above is a photo on the summit, not looking toward the base, but it's the best one I took regarding snow conditions up there. I didn't take my SLR, just a point/shoot with 28mm-280mm equivalent, so I don't have any significant base pictures from this trip, though I did get great reconaissance shots of the peak north of Tikaboo, with the snow helping to outline the topography of it.