I talked with a friend who works in Fresno and he told me there has been changes in the radio system. He is not a radio guy so I was only able to get limited info. It seems they used to simulcast med 11/12 with both dispatcher and units. Now, only the dispatcher is being simulcast while the units are only heard on their respective channels. While googling this, I found this document that lists some some additional freqs and what looks like changes in units using those freqs. I don't know if this is the answer to your problem.
Haha on the way out the door I ran into one of the medic crews who had just dropped off a patient and totally forgot to ask him. It was just one of those days, but like I said, occasionally I hear ground units, so Im guessing its either something with their handhelds or vehicle radios. I do know that some agencies are able to go to a "direct" transmission, but I have no clue how that works. I wont forget next time
Okay so I talked to one of the medic crews tonight and he said that they were having some radio probs, but didnt elaborate. I told him what I had heard and he said that it flip flops between med-10 and 15. But as far as any changes he said he hadnt heard anything.