I can't answer your question. I can, however, give you some pointers that may help you figure it out.
On my 2012 GT, the factory fog lights attach to the back of the grille, via mounting points that are molded as an integral part of the grille.
I bought a 2012 Boss 302 grille, on which the "blank-off plates" are not separate pieces as you show above -- the whole grille is a single molded piece of plastic. Also, the dummy openings are a little smaller in diameter, and a lot deeper, than on the stock GT grille. Lastly, there are no mounting points for the fog lights molded into the back side of the grille. So for me to use the Boss grille and retain my factory fog lights, I'm going to have to both open up the dummy openings AND figure out some way to mount the lights. I'll also need to make sure there is adequate room for the lights between the back of the deeper Boss openings and the radiator.
On your 2013, you'll need to figure out how the lights mount (to the grille? to the car itself?) and see if the same mounting system will work with the Boss grille (if the lights mount to the grille, does the Boss grille have the same mounts? if the lights mount to the car, are the clearances the same?).
There is a different version of the 2012 Boss grille that has mesh covering the dummy fog light openings, for additional ventilation. That may be the reason the plates on the 2013 version are removable.
2012 GT Premium Coupe | Performance White | 401A Charcoal+Grabber Blue | Comfort Pkg | MT82 | Boss 302 Shift Knob | 18" Pony Pkg Wheels w/Brembo Pkg Center Caps | Boss/CS Front Valance | Scott Drake 5.0/Tri-bar Fender Emblems | FRPP Strut Tower Brace | Redline Hood Struts | GT500 Rear Splash Guards | Rear Spoiler Delete | Sound Tube Delete