I've been into cop shops twice (vic) to ask for a breatho, both times they were very reluctant, but after a chat and assuring them I hadn't drunk at least an hour or so previously, they did test me. Neither time would they give a reading though.
Always thought it was odd, the logic they use is that if I get pulled over 10 minutes later and blow over, they can get in to hot water. Odd thing is that I could drive through 2 breathos in one night and have the same trouble.
Pisses you off, you just try do the right thing, but they don't allow it. Strange.