Don't they share the space with California Public Radio? Seems to me there's some other public radio entities that use it.
Well, first of all, AFAIK there is no such entity called "California Public Radio". Most of the pubradio outlets in California, small and large, don't get along with each other terribly well; they're all fierce competitors. (except in Santa Cruz/Monterey, where it's just a hot mess of politics) Plus California's too big, too diverse, and too provincial for any one entity to realistically cover it all; branding-wise it'd be counterproductive because listeners in San Diego don't care about (and don't want to be associated with) Los Angeles, nor the Riverside area, nor the Inland Empire, nor the Bay Area, nor the Central Coast, nor the Jefferson region. Often the politics are kooky but there's a lot of good arguments for breaking California up into three or four states; that's how big and diverse it is!
Anyways, to answer your question, NPR West does not really share studio space with anyone. Certainly none of the area radio stations (KUSC, KPCC, KCRW, etc) have studios in the space. Nor does Marketplace, which is not in KPCC's studios up in Pasadena, but instead has their own offices and studios in downtown, near Dodger Stadium. MP existed long before KPCC came around in its current leased-by-APM form.
There ARE some entities that have temporarily leased space from NPR West over the years, or NPR initiatives assigned to there. I think some of the NPR Ahora (Spanish language) programming came out of there for a while, but don't quote me on that. I have a vague recollection that when Fresno-based Radio Bilingue was doing that CPB-funded experiment (which kinda failed because they could never get a AM/FM outlet in LA proper) they were trying to coordinate local stuff through NPR West, too. But there's never been anything really huge and/or permanent at NPR West to my knowledge.