I am in the process of trying to update and add bus stops and bus routes in San Diego County. The majority of current bus-stops are based on old data and are many are just a single located at an intersection. MTS and SANDAG have new SHP layers and update this information quarterly. I am approaching this in pieces so as to not break any functionality of the existing bus routes in OSM. However, from what I have seen, the vast majority of bus stops need to be changed and many routes are not added yet.

http://www.sangis.org/

TRANSIT_STOPS_GTFS Publication Date: 2017-06-28 Summary: Public transit stops and stations covering the County of San Diego. Bus, commuter and light rail, and trolley stops managed by the San Diego County Metropolitan Transit System (MTS) and the North County Transit District (NCTD). Data is developed from the General Transit Feed Specification (GTFS) data available from the transitland feed registry (formerly from the GTFS Data Exchange). Layer is updated quarterly and may not reflect most current route information.

TRANSIT_ROUTES_GTFS Publication Date: 2017-06-28 Summary: Public transit routes covering the County of San Diego. Bus, commuter and light rail, and trolley routes managed by the San Diego County Metropolitan Transit System (MTS) and the North County Transit District (NCTD). Data is developed from the General Transit Feed Specification (GTFS) data available from the transit land feed registry (formerly from the GTFS Data Exchange). Layer is updated quarterly and may not reflect most current route information.