The construction of the Ethernet cable does a lot to protect it from the "noise". I am aware of a number of installations with standard Ethernet cable in the MCC wireways for PLC control of the equipment and I have heard of any noise issues.
We have Profibus running into ASD's and still not problem and of course all over the MCC, a drop in every cubicle where the shielding is discontinued for short lengths where the termination is made. The protocoll has various interference rejection and signature validation features and that takes care of most issues.
Sometimes noise rejection lengthens update intervals as the same bit-stream needs to be re-sent several times. But of course the traffic limits are set that the update will still be above the lower limit.