Trucks are legal on I-280, but on the Pennisula have generally used US 101 instead, probably because it's more convenient for most trucks (closer to most businesses). Of course, I-280 also goes by downtown San Jose and becomes I-680, but even there I don't recall see a particulary large number of trucks, unlike I-880.

On I-580 from about Hayward to somewhere in Oakland, trucks are illegal, but from Hayward to I-5 trucks are, well, extremely common on I-580.

There are other metros areas with restrictions on trucks and non-carpool vehicles, the most extreme I can recall is I-66 in Virginia goes all HOV (yep, all lanes) during rush hour once it reaches the beltway.

Tony