Again, Will with the zone designations you're talking "survival" not plants actually thriving and being beautiful. I always think when I see "zones 4 to 10" on a plant label that this plant will most likely do best in zone 6 or 7 but it doesn't tell you that.
So lots of things that grow outdoors here (I'm almost in zone 10 for what it's worth) do experience temps down into the 30's occasionally - that would be maybe 3 or 4 winters of the 15 we've lived here. The plants "survive" but were significantly slowed down for a year or two afterwards so there was damage they wouldn't experience in an indoor controlled environment.
Just a thought on the juniper as a houseplant idea - couldn't you just put the juniper outside for the winter to give it the cold dormancy it wants? Maybe a bonsai in a very small container would be more frost sensitive, but in a protected spot? It might be worth a try, if you really wanted to grow such a plant indoors.
Speaking as a dedicated pusher of zones here . . . can you tell?
