where do they collections declare that they are queryable?

[Casey Link]

> Or where does CollectionManager figure it

check: CollectionManager::queryMaker()

You'll see a line like:  if( pair.second & CollectionQueryable )

It's using bitwise flags to determine the various Status' of a
Collection. If you grep for "& CollectionQueryable" you'll see the
various methods in which it is tested.

Casey