I have a 1760 acting as a H323 gateway, IOS 12.2(15)T IP VOICE (PLUS?) feature set, and a VIC-2FXO both ports directly connected to the PSTN.
All works fine, except we have received complaints from the client, that they loose the lines when the router is powered off/on. When I checked (I only have remote access unfortunately) the fxo ports were off-hook, athough no calls were made, and when calling from PSTN side, the PSTN reported number unavailable or something similar.
there were no reports of FXO ports hanging after conversations, so hangup works as expected (I suppose) -- it worked as expected, when tested, that's for sure.