Here's the latest from the New Jersey Supreme Court on the power of railroads to take property, and when land is already being put to a "prior public use" and thus immune from being taken.
In Norfolk Southern Railway Co. v. Intermodal Properties, LLC, No. A-117-11 (Aug. 6, 2013), the court held that the railroad had the power to condemn an adjacent parcel already used as a parking facility to expand its rail facility to, among other benefits, provide more parking space. It's a long opinion (42 pages) so we won't go into it in great detail, so here's the short version.
The court held that the statutory requirement that a railroad's condemnation be "not incompatible with the public interest" was met. Although the taking was for parking and the property taken was already being used for parking by its owner, this did not qualify as a prior public use because the parking was not public. Moreover, the owner Intermodal did not have the power of eminent domain, and an owner invoking the doctrine must have the power.
The court also held that New Jersey's statutes, which give railroads the power of eminent domain in circumstances "as exigencies of business may demand," means that they may take property as the needs arise in the ordinary course of business. The court found the current use of the term (emergency, urgent, or immediate) are not consistent with the way the word "exigency" was used when the statute was adopted more than a century ago, and it is the meaning of the words at adoption that control.
There's a lot there in the opinion, although most of it deals with the details of New Jersey's statutory requirements. But it is a good primer on the prior public use doctrine so is worth reviewing just for that alone.