I doubt it. Those electronic shelf labels (ESLs) are PIN protected for the pairing process. If you steal them from another store you can't pair them to your ESL network if they've already been paired before.
You'd need the PUK from the manufacturer based on the device S/N to unlock them first, but the S/N of each device is tied to the store that bought it so the manufacturer will know it doesn't belong to you and not give you the unlock PUK.
Plus, at the kinds of volumes retailers are buying ESLs, I doubt they'd go through all this trouble to pair a few stolen units.