Comment 140 for bug 304889

No, telepathy-haze is just another Telepathy Connection Manager. Read the text you just shared:

Haze: A connection manager based on Pidgin's libpurple, supporting all protocols in Pidgin (AIM, ICQ, Yahoo, MSN, etc) at a basic level, but already very usable.

libpurple uses GConf's system proxy settings, which contain authentication.

And you have been told wrong, here's a screenshot with the latest gabble not working (latest glib, with glib-networking, with libproxy support):
http://people.freedesktop.org/~felipec/gabble-proxy.png

See?

Works fine with libproxy-simple though.