Our band version is in concert G Minor (I'm led to believe this is the original key) and the Lake band version is in concert C Minor.
The Lake Eb solo part is the same as our Bb solo part, so it is their band accompaniment that has been written in a different key, not the solo part.
As mentioned before, if you want an Eb solo part to go with our version of the accompaniment then please email or send a PM.
While doing my research, I discovered another version for 12 Bb trumpets!
http://www.triplo.com/goedicke.html