The trial court did not abuse its discretion in finding that plaintiff’s suit was the catalyst that at least in part caused the city to increase its land use plan’s allocation of areas for low cost housing to satisfy its regional allocable share of the county’s affordable housing needs. That was true even though it took the Legislature enacting a new law that removed the exemption for charter cities, like defendant, and a suit by the state’s housing agency to finally force compliance. Plaintiffs’ suit initiated all of that action and in any event only needed to be a substantial factor not the sole cause of the city’s changed policy. The fee award was otherwise proper in that the other requirements of the catalyst theory and private attorney general statute were satisfied.