Hardly. You have several options here, and since you said you have dumped all the original programming to ARC-XT, you have a working connection between the computer and scanner.
You can;
a. Get a premium subscription and download the data you need from our database. You can find out about this by going to the blue toolbar at the right under the Scanner Master ad, float your mouse over About then select Our Premium Services .
b. Get an updated Pittsburgh file from someone in the Pa. forum
c. Download your current programming into ARC-XT. Then use ARC-XT to restore the Pittsburgh data from the backup you made. However to me this is sloppy...and you would still need to adjust the data for whatever changes has taken place in the time between when the data was originally loaded to the scanner and the present. Not the best option, to me...
Anyway, in each case, you could keep the Pittsburgh and Philadelphia stuff separate by assigning them to different Quick Keys; then simply enable/disable one or the other when you need to. There's a fair amount of territory between Philly and Pittsburgh - you are likely already familiar with your route, so you should know which county data you would need to load up. In fact, if I were you, I'd get a GPS and use Location Based Scanning to select each system (again, isolated by Quick Keys) as I went. No leaning over and fooling with manual selections that way...
You would really need to understand how DMA works for this...I would start with our online FAQ; the first couple of topics will get you going. To get to it, go to the blue toolbar under the Scanner Master ad, float your mouse over Wiki, select FAQs and select the Uniden DMA FAQ from the list.
73 (best regards) Mike