I've fermented sorbated cider every year for the past 3-4 years. Except for last year when I got some fresh-pressed cider. Sorbate does inhibit yeast reproduction but not fermentation, so if you have a big enough active yeast pitch, you can overwhelm the inhibition. Here's how I've done it:
1. One method is just use the whole yeast cake from justfinished fermentation.
2. Another method is to do a Graf. Start the beer portion fermenting a day or two before you add the cider.
3. Third method is to start 1 gallon of non-sorbated cider or apple juice fermenting, then add the sorbated cider a couple days in. This is what I did this year- I found the Honeycrisp nonsorbated cider mentioned above. Started 2 G of that fermenting with WY1450, then 2 days later added 3.5G of sorbated Macintosh cider. I started it back on 9/30, and just bottled it 3 days ago. OG was 1.054. FG=1.006. Flavor was pretty good.