I believe this snowmobile crossing was part of the compromise that allowed for the Hoover Wilderness Additions (mostly the Walker River north of Dorothy Lake Pass) to be included in the recently passed wilderness legislation. As part of this compromise, the Leavitt Lake area was excluded (but is still a WSA), and will be essentially managed as wilderness in the summer, excepting the Leavitt Lake road itself. Here is the currently proposed snowmobile corridor, which is just south of Sonora Pass:
http://www.fs.fed.us/r4/htnf/projects/bridgeport/PCTXing_NOPA_2010-06-25.pdf.