Comment 2 for bug 770464

User authenticates not on host but on realm. And one host can have many realms. I don't understand why did you decide to use indirect signs for authentication (you try to detect realm via host) instead of direct signs. Why don't you want to add one more optional parameter 'realm' to authentication.conf?
Ok. I did two test, they are in attach. Both of them had the same output and logs with and without http_proxy params in bazaar.conf.
First one without any info in authentication.conf.
Second one with following sections:

[subversion.mycompany.net]
scheme=https
host=subversion.mycompany.net
user=danilov
password=xxx

[subversion.mycompany.net2]
scheme=http
host=subversion.mycompany.net
user=danilov
password=xxx

[https_proxy]
scheme=https
host=wpad
port=8080
user=KDanilov
password=xxx

[http_proxy]
scheme=http
host=wpad
port=8080
user=KDanilov
password=xxx