A cool sunporch with temps that stay above freezing would work. Since the plant is considered reliably hardy only to zone 9, you'll need some type of protection beyond what you're already considering.

Try a google.com search under tibouchina urvilleana.

Softwood cuttings are relatively easy to root.

Tibouchina is not one of the subtropicals that will reaact well to forced dormancy in unheated, unlit conditions. As Eric mentions, it would do considerably better if placed in a cool sunporch over the winter, where it gets bright light and can be kept above freezing. It easily tolerates the occasional light frost here in northern California, and will continue blooming all winter long as long as the night time temps generally stay above 40F, and will come back from the roots if well established in the ground, at temps at least down to 24F. It will tend to burn all foliage off and lose most smaller branches at temps which will also freeze Brugmansia. Your salvation my come in the knowledge that it responds well to hard pruning, and can be cut back to the ground here and regrow rather rapidly in one season, once it warms up again and is goosed with the proper fertilizer. So if you need to cut it back to bring inside, you can safely do so, but don't try to force it into winter dormancy, it just won't work...

Need Help
Not easy to find information on this plant?
Would like too start from seed. Any idea on time?
Will it be easier just too find some rooted cutting?
Did some soft wood cuttings in August did not have success.