In the environment you state EMT shouldn't be necessary...of course AHJ had the final say so. I'd use EMT just to protect the cable from user abuse!
For example, BERK-TEK's LANmark-350, Category 5e+, Plenum UTP Cable spec sheet shows that it is rated for -20º c - 60º c (-4º f - 140º f)
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Spec Sheet]
You can always check on the manufactures spec sheet for the brand and type of cable you are using.
Then again this has nothing to do with your OP. Just use outdoor rated parts and you shouldn't have any issue.
