Hello, Jean!

As a railroad aficionado, this is an aspect of property rights law that I have always found to be very interesting, since much of our state's history is tied to the railroads.  In fact, the old Pennsylvania Railroad main line runs through several of the counties I cover.

The traditional doctrine concerning the use of railroad easements and rights-of-way was that there could be no expansion of use beyond what was contemplated when the easement was originally granted.  In other words, use of the right-of-way was limited to the use necessary for the operation of the railroad itself (the "limited-purpose easement" you mentioned).

In recent years, however, the courts have applied a doctrine of "incidental use", which basically states that a railroad may grant an easement within its right-of-way without obligating itself to compensate the owner of the underlying fee interest, so long as it imposes no new burden inconsistent with the original use of the easement.  Incidental use has been successfully argued by telecommunications companies seeking use of railroad rights-of-way for the siting of their digital cable lines.

There is also a "shifting public use" doctrine, which anticipates both societal and technological advancement and development.  The rationale behind this is that since most railroad rights-of-way were established thorugh either state or federal legislation and/or condemnation, their subsequent appropriation to another public use does not necessarily require additional compensation to the owners of the underlying fee interest.  Even so, the overall burden on the fee owner must not increase beyond what was contemplated by the original right-of-way grant.

Great topic.  Keep us posted as to how this plays out.

Regards,
Scott Perry