The Green Party of California (GPCA) adopted these rules in 2000. The rules are described in the GPCA bylaws. The rules are based on the description of STV found in Electoral System Design: The New International IDEA Handbook, except that GPCA uses a fractional threshold, and does not elect candidates that do not reach the a full (static) threshold.
Neither IDEA nor the GPCA bylaws specify a method of breaking ties. This implementation breaks all ties randomly. See Jonathan Lundell's paper Random tie-breaking in STV for the rationale.