I think Fire-based EMS can and does work in smaller departments.... If your FD has fewer than 5 stations, and has as many staffed ambulances as staffed engine companies, with staff rotating from suppression units to transport units, it makes sense to have fire-based EMS.
Pittsburg is NOT a small city; its EMS department does more than just treat and transport patients, and it's done it well for decades. It's not a small city, nor would it be a good candidate for fire based EMS. This is another example of the FD wanting more money to expand their duties, instead of the city allocating more funding to the current EMS system to expand operations.
Many major cities have taken over EMS with big promises, pushed out their independent EMS systems, and ended up not fulfilling any of their promises, but since they destroyed the previous EMS system, they have no options other than to understaff and underfund EMS or outsource to a 3rd party. It's a story that has been repeated all over the US multiple times.