|When is the best time to transplant butterfly bushes. They seem to be still dormant.|
|I should mention that your zip code places you in zone 5A or the coldest part of winter hardiness zone 5. In a windy or exposed location it could actually be as cold as zone 4. Butterfly bushes are reliably winter hardy in zone 7 and usually root hardy into zone 6. For this reason I suspect they may not have survived at all -- for the best chance they would need to be growing in a sheltered spot with wind protection and very well drained soil and also be heavily mulched in late fall.
You can check for live wood by beginning at the tips of the branches and working your way down the plant. Live wood will be a bit supple (not much) and have green inside the bark, it should have some plump buds beginning to swell also. Dead wood will be brittle, off color tan or gray, and will snap in your fingers. Sometimes gardeners in cold areas end up trimming down to the ground, but the plants regrow from the base and bloom during the summer.
After all that, butterfly bushes usually do not transplant very well because they are so deep rooted. If you want to put one in another spot, you would probably have better luck planting a new one. I'm sorry I can't be more encouraging.