It's not something that's been suggested to my knowledge and geochemically it's missing some of the hallmarks. There are suggestions of isolated slab window related magmatism in the Tahoe region (e.g., Cousens et al., 2011), but not Long Valley. Long Valley is generally associated with other magmatic systems in that part of the western Greater Basin. Their exact origins are a bit enigmatic but are largely inconsistent with slab window volcanism seen elsewhere.