Interest used to earn investment income is deductible (aside from RRSP), so yes.
The above link is crystal clear on expense vs. capital. With CRA, take a position that is defensible and ensure it passes the smell test. There is no written rule, but generally items under $500 are expensible and worthless to track in a CRA class.
In your situation, I am 99.9% positive it is a capital expense as you classified it an upgrade and therefore should be added to ACB of your property.
"I believe that banking institutions are more dangerous to our liberties than standing armies. If the American people ever allow private banks to control the issue of their currency, first by inflation, then by deflation, the banks and corporations that will grow up around the banks will deprive the people of all property until their children wake-up homeless on the continent their fathers conquered."
-Thomas Jefferson 1802