How do Smokestacks of Gnaak and Mirror Realm interact?
By the time Mirror Realm enters the realm, it's already a copy. Thus, it can copy a nearbysite, and then promptly loses all abilities of that copied site (but still is the copy, without abilities). See 'Apply Ongoing Effects In Order' in the codex for nitty-gritty details.
How do Smokestacks of Gnaak and Rift Valley interact?
Rift Valley enters the realm using its ability, and only loses its ability once it's in the realm (which by then, it doesn't really matter).
