Is it feasible to use Bay Area express lanes for no charge as HOV-4 (or discounted bridge tolls) in a rental car? It looks like you can't use the license plate option to get HOV rates. As far as I can tell, the Avis-provided, charge-an-absurd-surcharge ones also don't support FasTrak Flex for HOV usage. Is that right?

It also looks like I can buy a transponder if I go to the right place (though that won't be trivial), but it includes $25 of pre-paid tolls, whereas we don't expect to pay any tolls; we just need it to use the express lanes for free. Am I missing a good option here?

(We'll be landing at SFO mid-afternoon, just in time to catch the heart of rush hour traffic, and driving to Yosemite. We're deciding between renting at SFO and taking BART over to Oakland and picking up a car there; either way, it looks like the I-580 express lanes may help. Is it worth any effort to be able to use the express lanes eastbound at 4:30 or 5:00 on a weekday afternoon?)