When do Banks Reject Powers of Attorney for Property?

Many Canadians do not have powers of attorney in place – but what about those that do? Are these powers of attorney drafted in such a way that financial institutions will accept them? At least in the attached article the grantors still had capacity and could take steps to fix the issues. The most difficult situation to address is where the grantor no longer has capacity, and cannot amend an existing problematic power of attorney!
http://www.cbc.ca/news/canada/story/2012/11/09/bc-bankingdenied.html?cmp=rss&goback=.gde_2411490_member_189559030