Can I tieWrap A Cat6 to the outside of an EMT Conduit?

The answer by @C_kayak_run is correct: you cannot "hang, tie or otherwise support" anything from an electrical conduit, other than control wires for the same device powered via the conductors in the conduit. The NEC Handbook even says it is PRECISELY because of the designed heat dissipation of the conduit, and the mechanical hangers which are not allowed to support ANYTHING other than conduit.

This would be a violation of electrical code and thus fire code and building code, meaning your insurance company will add it to the list of violations they find when ANYTHING goes wrong inside the warehouse and you have to file a claim of any kind.

If you're "lucky" the fire inspector won't catch it and cite you for $200 a day until it's removed.

Per NEC and NFPA codes, no. Your inspector will probably require you to remove it. Article 300.11 (B) of NFPA 70 does not permit anything to be attached to conduit, with one exception: Class 2 control cable may be attached to the conduit if it serves the circuit in the conduit. Apparently, the concern that NFPA has is heat from the electrical conductors inside the conduit may not dissipate adequately if there are additional cables and wires tied to the outside of the conduit. While it is highly unlikely that a single low voltage cable that is wire-tied to a conduit would cause a problem, I guess it is logical that many wires and cables could be a problem. The question is where do you draw the line? I guess NFPA draws the line at one (1). So, I’m sorry to say, you will have to remove all the wires and cables from conduits in order to be compliant with the Codes.

The Cat6 cable has a shield to protect it against electrical interference. Also, the conduit is grounded.

yep