No, I don't think that's squirrel tail; it's probably bucktail (which is what the Brad's calls for) but it kinda looks kinkier, like deer. Personally, I think it is simply a "Tyer's Imagination". Judging by the old-school but not super old-school ribbing, I'd guess this fly was tied up in the 80's.
Hogwrangler actually found out what this was called for me, it's a pattern called The Mover originated by Tim Coleman. Here's the recipe: Tag-Gold Oval Tinsel, Body-Claret Floss, Ribbing-Oval Gold Tinsel, Wing-Red Squirrel Tail, Collar-Natural Lemon Woodduck Flank followed by shorter Guinea Fowl dyed Claret.