CA Health & Safety Code Section 5472.5

The rates may be collected with the rates for any other utility service furnished by a department or agency of that entity over which the legislative body thereof does not exercise control, or with a publicly or privately owned public utility, with the written consent and agreement of that department or agency or public utility owner, which agreement shall establish the terms and conditions upon which the collections shall be made. The agreement, in the discretion of the department or agency or public utility owner making the collections, also may provide that those rates shall be itemized, billed upon the same bill, and collected as one item, together with, and not separately from, the other utility service charge.