Woops, there is a difference when initiating the two calls I described above. A PSTN call from the desktop gmail call widget is a voice-only call. Google talk presence musn't be enough to notify Google voice that I'm online. Monitoring dbus system and session is just silent in that scenario.

Like an earlier poster, in Pidgin I'm using an XMPP account configuration. That code needs to be looked at for a possible telepathy plugin fix. The default jabber plugin should work, but I have yet to successfully sign in to a Google server. Someone with more knowledge should be able to produce a configuration or code fix in less than a day. I only have the next half hour.