I have been able to use a generic SIP based soft phone with TBB.

I'm using X-Lite which is available free from CounterPath.

The method is a bit of a kludge, but it works.

Here's how I did it:

•register for a free DID(telephone number), I got one from STANAPHONE, but others offer them as well (IPKALL) setup your soft phone to connect to it.
•Configure this DID to be your remote phone, and enable remote phone.
•now if you click on a number in your portal directory, your soft phone will ring and you will be connected to the number you clicked on.

Of course you can just use the remote phone if you have access to a direct line, but if you are in a hotel with a switchboard the above procedure works great. It also allows anyone to call your soft phone directly with your DID or your TBB #.