Theoretically... anything that's a matter of public record is supposed to be available.
In actuality, it could depend on how honest the agency and its employees are.
Initial 911 calls
Computer Aided Dispatches
Telephone calls to the dispatcher
no calls from officer to officer though, at least if they're using personal cellphones.
I have found out though, that it Does matter who or what part of an agency you send the request to. I found out that where I live, if you contact the Dispatch Office (co-located with the Sheriff's Office) all you will get back is an incident report. If you want full transcripts you have to go through the County Manager.