You may have already seen this...
Force IE compatibility mode off using tags
This response in particular may be of interest...
"I have found that this does NOT work if the user (or the sysadmin) has turned on compatibility mode as a default by going to Tools->Compatibility View Settings, and checking Display all websites in Compatibility View. To fix the problem, I have to return the header in the HTTP response: X-UA-Compatible: IE=edge" – speedplane Apr 19 '13 at 11:29
Also...
"Word of advice for those who find this answer, but are unable to get it to work for them. The compatability meta tag MUST be the first meta tag, and there can be NO IE conditional statements before the tag." More: tesmond.blogspot.com/2011/10/… – Chris Sobolewski
Is your meta the first one on the page?