Sorry for the long post. Am I correct that my obligations stop at the property line?
This is not based on PA law as it is darn near impossible for me to access PA laws in general so I kind of gave up. This is based on general rulings and common law.
With an easement, barring an agreement contrary, you are generally considered to be liable for a pro-rata share of the costs of maintenance of the easement. That means if you both use the entire easement, you are both liable for 1/2 of the total costs to maintain the easement.
Your liability does not stop at the property line. In fact, you can almost think of it as it starting once it goes onto another's property. You are using their property and causing damage to their property. It is only right to expect you to be liable for the costs to maintain the easement.
I am not an attorney and any advice is not to be construed as legal advice. You might even want to ignore my advice. Actually, there are plenty of real attorneys that you might want to ignore as well.