What does it mean for my Canadian Old Days Pension and Canada Pension because of a treaty between US and Canada taxes due can be deferred. how does this work?

I have attached a link to the US/Canadian Income Tax Treaty.  Under "Tax-deferred plans", the treaty states:

"Tax-deferred plans. Generally, income that accrues in certain Canadian retirement plans (including RRSPs or RRIFs) is currently subject to U.S. tax, even if it is not distributed. However, a U.S. citizen or resident can elect to defer U.S. tax on income accrued in the plan until the income is distributed.
The election procedures differ depending on whether an individual qualifies as an “eligible individual” as described under Section 4.01 of Revenue Procedure 2014-55 available at www.irs.gov/irb/2014-44_IRB/ar10.html."

Please see this link for more details:   http://www.irs.gov/pub/irs-pdf/p597.pdf