yep, provided the ground isn't waterlogged or frozen, should be ideal.

Agree, plant now unless waterlogged or frozen.

Shelter them until the soil warms. Cool greenhouse would be best, but not anywhere artificially warm. Unless they are bare root, which should be planted now, they will be happy enough in their pots for a week or two.
The risk of a cold spell is still too high, the soil will be too wet and they won't thrive. Best to wait until later in March when the soil has warmed up just a bit (and hopefully drained a little).
I say this based on experience of B. davidii but I am sure the others have similar needs.