You do not have to file in PA unless your employer mistakenly withheld PA state tax from your pay (PA in box 15 of your W-2 and an amount in box 17).
However the reciprocity agreement, between PA and MD, does not apply to local city taxes. You are not required to file a PA city return, but you are also not entitled to a refund of the city withholding (box19 on your W-2), unless there was an error in the amount (highly unusual).
