09 Ego's came with Shaft 3 barrels, which are interchangeable with Shaft 2 fronts and backs. Shaft 2/3 are not interchangeable with Shaft 1 or 4 parts.
As for using different brand tips on a Shaft back, I don't think there is much, if anything you can use.
There were talks of Deadlywind making tips for them, but due to the diameter and how the Shaft3 joint is (male threads on the front) the DW tip would either be very weak or a large portion of the ID bore would be aluminum instead of CF. So the idea was scrapped.