Tieball
Masterpiece
If you are going to slip that tight root ball into a larger container of different soil you might achieve a better end result by loosen the rootball sides gently. Tease the sides slightly and free up a few roots. When planted together....the old soil and the new soil begin to blend. This will help create some transition soil areas.
And.....take care when watering. With those two types of soil....current hard soil with compacted roots and open nicely draining soil....the water will naturally flow through the free draining soil and your rootball might remain unwatered...dry for the most part. The water develops "channels" and flows through those channels right to the drainage.....out of the container. I handled this problem with a tree once by putting my container in a larger round dish pan with no holes. I watered until the water drained out of the container into the dishpan. Then continued watering until the water level in the pan was about one third the height of my plant container. I just let it sit there awhile....so roots could find water naturally before gravity took the water away. I suppose it is similar to submerging....but I liked the siphon action that happened between dry and wet soil masses. It worked well for me.
You might take a rounded end, chopstick like tool, and periodically poke at that solid rootball around the tree....a little ways away from the trunk. I mentioned rounded because a point would more likely penetrate and damage roots...rounded sort of helps the tool move around objects rather than cut through. Be like a bird poking around for insects. You will begin to break the soil up....continued watering will settle in those loose areas and begin to provide moisture...breaking up the soil area slowly without root damage.....and this will help a lot later when you want to clean old soil off roots and plant your tree in a new container or good soil.
