I have an XC and just put an EC rear fender on my bike (my dealer ordered the wrong part). The only difference between the two fenders is a hole on the right side for the taillight wiring to pass through, and mounting points for the license plate support.
So yes, they will swap.
Jeff
BTW, as you may be aware - if it's just getting rid of the taillight/plate holder that you're after, you can unbolt them and have basically the same thing as an XC fender.