I do believe it is possible ogammo,
You would use all the SIP settings and your SIP URI is
1519XXXXXXX@voip.freephoneline.ca -- or whatever your phone number is....
1+yourphonenumber@voip.freephoneline.caI haven't tested this so I am just going off of what I use for my Polycom 330 IP Phone at the office here.
Ensure that you put your SIP password in the correct field and if your phone doesn't have it I don't think it will work, since our voip server is locked to ensure that until you buy the config file you can only use the softphone.
Thanks.
Ps. Auth ID and Auth Password do NOT have anything in it -- This will require you to dial a password whenever you dial out and to be perfectly honest it doesn't always work that way.