As with the Nanoracks/Lockmart one, there is no discussion of orbital location. It looks like Sierra has decided to team up.

[Tuesday-morning update]

OK, here’s a description from NASA Spaceflight. They clearly want to be co-orbital with ISS, but they say that they’ll be at a higher altitude. That doesn’t make sense, because if they aren’t at the same altitude, the nodes are going to drift apart and while they’ll be at the same inclination, they will be in a different orbit plane. They should be leading or trailing it at the same altitude if they want to stay co-planar.