Storage fees as a business deduction?

A lawyer retired after 27 years.  As required by her professional liability insurance company, she had to retain client files.  CRA initially disallowed the deduction.  The Tax Court found that she had built into her client fees a certain amount to cover the cost of storage.  As she had reported this income, it was only fair she be allowed to write-off her costs now.  The Tax Court also felt the amount claimed was reasonable.