You are confusing what's right for in-ground trees and what's possible for containerized trees. Winter is much different for the two.
As for the mechanics of how trees overwinter, Brent Walston's website has an extremely well written articles on this.
http://www.evergreengardenworks.com/overwint.htm
Your blanket assumption for dormancy hours is not accurate. It varies tremendously among species.
Your assumption that the ground soil doesn't get cold below 1/2" down and thaws before 10 is a little naive. Soil doesn't have to freeze to be cold. The ground is also a vast temperature sump--it is slow to warm and slow to cool--it's average temperature (at various levels) lags behind air temperatures by weeks, even months. Ever dig a hole in March? the soil six inches down --at least here in Zone 7 No. Va.--can contain ice particles--even on a 65 F day...at that time of year.
Daytime temps above forty degrees with freezes at night are not a good thing for trees in containers, as they lack the soil volume that in ground trees have to protect them from extreme temperature swings. They are extremely vulnerable to freezing and frost in late winter--they are completely vulnerable to freezes if new leaves are present. A hard freeze on a newly repotted tree that has new growth can kill the entire tree, not just the new leaves.
You cannot change a tree species' basic genetic environmental limits with "acclimation." Trees grow as they can--or can't. Pick and choose which species you grow with that in mind.
Local species will ALWAYS be hardier than species from somewhere else.
In-ground trees are protected (mostly) by their "chilling hour" requirements. They cannot bud before those requirements have been reached. Each species has a different requirement generally. Dormancy break, unlike the onset of dormancy (which is spurred by shortening daylength)--depends on soil temperature. Once soil around all around the roots rises above 40 or so, the tree begins to grow. This can take quite a while in nature, as the ground -- surface to 12 inches down,--the root zone--is a deep volume of soil. The temperature of such a vast volume of dense material doesn't change easily or quickly--even if air temps do. Even if air temps are in the 70's for a few days, the soil around tree roots 8 inches down isn't going to get much above 40 in Jan. Trees have adapted to this to avoid early bud break during warm spells in the winter. That's why you don't get spring during a warm week in January.
I wouldn't be planting trees this time of year. It might be "OK" to do it. It could also mean death for the tree if a deep cold spell comes along (which this year isn't out of the question). It's not really about being "OK" to plant anytime the ground isn't frozen. It's more about when it's "optimal" or "ideal" to plant. OK doesn't really cut it.