A regulated party has standing to challenge the regulation.
Question is ripe, as possible future displacement of a utility's approved projects due to the change in the cost allocation scheme's structure is conceded by all parties, and further factual development wouldn't speak to the question of law at issue.
Claim first made in Article III review that the agency impermissibly shifted the burden of proving reasonableness to the utility needed to be exhausted in the pertition for agency review.
On merits, Commission's ruling that already-approved projects needed to be revisited in light of the regionally interconnected projects was not arbitrary or capricious, as there are public policy benefits from that sort of thing, and proper accounting for the interregional projects requires integration of the costs of the already-approved projects.
https://www.cadc.uscourts.gov/internet/opinions.nsf/6440A9564E36D841852582B4004FED20/$file/16-1150.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.