Exchange 2013 - Import-TransportRuleCollection from Exchange 2007 failing

I am in the middle of a Exchange 2007 SP3 to Exchange 2013 Sp1/CU4 migration and am importing transport rules and it's failing.

[PS] C:\Windows\system32>Import-TransportRuleCollection -FileData C:\2007TransportRules.xml -Verbose
Cannot process argument transformation on parameter 'FileData'. Cannot convert value "C:\2007TransportRules.xml" to type "System.Byte[]". Error: "Cannot convert value "C:\2007TransportRules.xml" to type "System.Byte". Error: "Input string was not in a correct format.""
    + CategoryInfo          : InvalidData: (:) [Import-TransportRuleCollection], ParameterBindin...mationException
    + FullyQualifiedErrorId : ParameterArgumentTransformationError,Import-TransportRuleCollection
    + PSComputerName        : ex2013-mb1.MYDOMAIN.local

Before you ask, I am still on SP1/CU4 because CU5 and CU6 are so buggy I refuse to install them. And that's probably not the fix anyway... WHEN IS CU7 coming out?