Tesla makes all-electric cars; no gas involved. HOV stickers are for all-electric cars only, now. I've seen them on Nissan Leafs.

The problem is the leaf doesn't have enough practical range to go from SF to Mountain View and back, and certainly not enough to do a full day of driving around the Bay Area. A roadster does, and a model s probably does, at least with the larger battery packs.

The yellow ones were for hybrids.

The white ones are for CNG, plug-in hybrid, or battery electric, and are good until the end of the world (or 2015, whichever comes first)