The Ghost Bear C3i project has almost certainly stopped. At least until we get futher XTRO Republic/Clans... In any event, even though Ghost Bears may have been willing to experiment with it, i doubt they'd go for adopting it really. At least not until they've seen others use the tech enough.
I'll note that even though ProtoMech using factions have EI, this does not mean they utilize it outside Protos. As warrior mentalities go, i feel like neither Horses nor Ravens are the type to use EI. Falcons? Sure. Wolves? Maybe. Ghost Bears? Too conservative. Mongol Horses, maybe, but i doubt other Horses are big on EI.
SharkFoxes undoubtedly conduct cost-effectiveness analysis and figure that EI probably isn't worth it.
As for selling it, while the opinion may be that it won't work for Spheroids, i doubt they have any issue selling a kit and lifetime supply of meds provided someone forks over the cash.
In any case, the Clans are probably mistaken about EI not working for Spheroids properly, unless it really depends on specific genes found on all Clan tankborn warriors. Which seems unlikely, and even then you probably can find people who carry the same genes thanks to shared ancestry and thus EI should work for them.
Not surprised at the Clans being mistaken though, they have somewhat weak grasp on sciences at times.