Legal Question in Real Estate Law in California

Yes. A partition action.

There is nothing in the partition statutes (Code of Civil Procedure sections 872.010 through 874.225) that prevents an action being brought against a co-owner, regardless of whether the co-owner is an individual, corporation, trust, or whatever. The only restrictions are that a partition action cannot be used against a spouse, and if the property is owned by a partnership the use of partition (rather than procedures under partnership law) is up to the discretion of the trial judge. So, yes.

Sure. The trustee of the trust will be a party to the partition action, but it does not stop it.