If you actually split the costs and all other information is in both names, then enter your percentage of the amounts into your return.
Check out our Blog post regarding splitting capital gains. It's not something you can just choose to do.
http://turbotax.intuit.ca/tax-resources/sbt-split-capital-gain.jsp
Very annoying that you have to do all this manually.
I have been reporting this deficiency every year to Intuit. They still have not gotten the message