You are exactly correct. In California, all autos with 2 or more occupants (3 in a few places), or motorcycles can use the HOV lane. Zero-tailpipe-emmissions vehicles can get a sticker that gives single occupant access until 2019. There is another sticker with a quota cap (these are about 1/2 gone) for gas/electric vehicles that run on battery for some minimum number of miles before their engine starts. I think alternative fuels vehicles are also eligible for this one. This sticker also expires Jan 1, 2019. Hybrids like the Prius used to get a sticker, too, but no longer. See http://www.arb.ca.gov/msprog/c...
So, yes, a Tesla gets the HOV sticker, too. But if all you want to do is get to and from work as cheaply and quickly as possible, the Leaf is perfectly adequate. If you want more range, or want to impress your friends, then the Tesla is for you -- if you have the cash.
Actually, here in Sili Valley it is a good place for electric vehicles. I see multiple Leafs and Teslas on the road every day. We have that magic thing called "infrastructure" -- charging stations at shopping centers and employer parking lots are actually relatively plentiful compared to most places. Multiple Nissan and Tesla dealers within a few miles. Then, too, we have climate going for us -- not too cold in the winter, not too hot in the summer -- so you don't have cabin climate control eating into your battery range. Plus, the Leaf's battery pack does not have cooling lines running through it -- Leafs in hot places have had some issues where batteries go to an early grave because of poor temperature management. A Leaf outside of a mild climate is a questionable choice.
I just got back from a couple of days in Minnesota where i did two 200-mile days in a rental car, driving mostly in rural areas, with day-time high temperatures of -2F. A Leaf would have been completely unusable for that trip. A Tesla would have been a risky adventure, assuming I could have strung together enough charging stations, which would have required considerable logistical planning.