they would not have drilled the hole bigger than needed for the siren wire. a siren wire is a ~16 guage wire, MUCH smaller than the 8 guage power wire he's talking about. If a decent installer did it, to fit a power wire through, he'd have to pull the grommet, re-drill and get a bigger grommet. Just do what I suggested in my above post and what Kyle seconded.
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