I can't advise you on Japanese Black Pine, but I can tell you from experience
that Kingsville boxwood does fine treated as a subtropical. Mine are in two
different group plantings with frost sensitive tropicals, so they are left
outdoors until the first frost warning. If they were alone they would be
allowed some light frost. During the winter they grow under fluorescent lights
with controlled humidity. If you don't have a light garden they will probably
do all right on a sunny windowsill in an unheated spare room.
Kingsville boxwood is very hardy, but your garage sounds perhaps borderline. I
think it might be safer indoors, since it does not need a full dormancy.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)