My guess:  it is related to a long-term improvement that will enhance the permanent value of the property, and hence you should capitalize and depreciate.  It would be a stretch to deduct as a current year expense, would be a red flag for IRS audits, and if the rental losses are suspended, probably doesn't make much difference anyway.

Are there concrete facts based on how the increase hike of special assessments should be treated?  I agree with the responder to this answer, but not aware of what this expense should truly be entered into the tax as?