Yes. You no longer own the property, so even if you didn't receive anything for it, you did dispose of it.
The Adjusted Cost Base is whatever you paid for the property, including buying costs like legal fees. etc...
The Proceeds of Disposition would normally be whatever you got when you sold the property. But in your case, you didn't really sell it, so instead you'll need to figure out what the Fair Market Value of your share of the house was when you sold it. You can look at what other, similar houses in your area were sold for, and use 49% of that.