So adding ro.ril.fast.dormancy.rule=0 to build.prop appears to do nothing on my HTC Desire, which is running a custom CM9 based build.
I spotted this:
Which works for samsung devices. But such a database does not exist on my phone. I assume its because samsung's RIL is quite different from HTC's one.
My assumption is that is not working as it has a H symbol consistently, and never changes to a 3G. I believe when i put a 2degrees sim in, it does change to a 3G symbol when idle, so fast dormancy works there. When disabled, i think it's meant to have a manual timeout after a certain amount of time?