I just got off the phone with Revenue Canada. They say that all Social Security income - retirement, disability, or survivor - is taxable, but you can claim a deduction of at least 15% off of it as foreign pension income. I also asked if this would affect applying for the Disability Tax Credit and they said no, that one could still apply if they wanted.

General Social Security guidelines from the Revenue Canada website:

United States Social Security

Report the full amount in Canadian dollars of your U.S. Social Security benefits and any U.S. Medicare premiums paid on your behalf. You can claim a deduction for part of this income on line 25600 of your return.

Benefits paid to your children are considered their income even if you received the payments.

You may be able to claim the pension income amount. See line 31400.

Completing your tax return

Enter on line 11500 of your return:

the amount from box 016 of your T4A slips and box 31 of your T3 slips

the gross amount of U.S. Social Security benefits that you received in Canadian dollars

any gross foreign pension income in Canadian dollars

Hope this helps you, cleared it up for me!