The mystery sites are a mystery because they are largely in areas where other utilities are the provider so there would seemingly be no need for First Energy subsidiaries to have any radio coverage. That's what caught my eye anyway. Time will tell....
Here are some images comparing FELHC (purple) and PA (blue) licenses.
Overlapped (both PA and FELHC licenses) - 5 locations
LANC33 - Truce PA (Lancaster)
WQVG945 PA - no FB2 frequencies - just 158.85 MO
WRBN333 FELHC - 153.4475 FB2 / 153.6125 FB2
SCHU03 - Keffers PA (Schuylkill)
WRBQ332 PA - 151.385 FB8 / 151.445 FB8
WRBN333 FELHC - 153.1025 FB2 / 153.3875 FB2
CARB01 - Albrightville PA (Carbon)
WQVL670 PA - 154.905 FB8
WRBP862 FELHC - 153.1325 FB2 / 153.5825 FB2 / 153.6875 FB2
WAYN33 - Orson / Mt Ararat PA (Wayne)
WQWM737 PA - 155.46 FB8 / 159.1275 FB8 / 158.79 FB2
FN:0008211143 FELHC - 153.3575 FB2 / 153.1775 FB2
BRAD31 - Canton PA (Bradford)
WQVA717 PA - 154.9425 FB8
FN:0008211143 FELHC - 153.5825 FB2 / 153.725 FB2
Non-overlap - FELHC only (as of 6/1/2018) - 8 locations
BERK04 - Port Clinton PA (Berks)
WRBP862 FELHC - 153.0725 FB2 / 153.44 FB2
DELA64 - Newtown Square PA (Delaware)
WRBP862 FELHC - 153.11 FB2 / 153.215 FB2
LACK53 - Archbald PA (Lackawanna)
FN:0008211143 FELHC - 152.2925 FB2 / 153.365 FB2
LANC01 - Cornwall PA (Lancaster)
WRBN333 FELHC - 153.08 FB2 / 153.455 FB2 / 153.6275 FB2
LEHI06 - Bowmanstown PA (Lehigh)
WRBP862 FELHC - 153.185 FB2 / 153.32 FB2
MONR03 - Mount Pocono PA (Monroe)
FN:0008211143 FELHC - 151.5425 FB2 / 153.1325 FB2
SCHU33 - Mahnoy PA (Schuylkill)
WRBN333 FELHC - 153.185 FB2 / 153.2525 FB2
WYOM30 Mehoopany PA (Wyoming)
FN:0008211143 FELHC - 153.4325 FB2 / 153.5825 FB2
Mike