The Institute for Justice, which argued the Kelo decision in front of the Supreme Court, has a pretty firm grasp on what should constitute an unconstitutional taking and the Institute has taken no position on Keystone because they don’t believe it falls into the category of an obvious private party to private party transfer - as was the case in Kelo.
see http://thinkprogress.org/climate/2015/03/01/3625804/keystone-kelo-eminent-domain-property/
The attorneys arguing FOR the actual pipeline disagree.
But that is irrelevant to the fact Cruz fought for the pipeline as a jobs program.