My volunteer corps has Captain, 1st and 2nd Lts. as far as command of crews and procedures on the road. Then we have president, vp, treasurer, & secretary for the building and administrative side.
On scene, its our corps officers that take command unless we are involved with other orginzations like FD where we each keep to our respected areas and check in with one another. With ALS, they pretty much command pt care but our officers are still there because lately we been on the outs with a few als units.