What is copied at the generation of child estimates?

The sub-contractors enter the costs into their own estimates and calculate the selling prices.

Allowing creation of child tasks at child level

The main contractor can offer this option. Task Sharing

Allowing changes in quantities and other fields

idem, ibidem

When a child estimate branches out into grandchild estimates, how are owners tracked?

The file tags are {child's owner name}{grandchild's owner name}

What should be avoided in the parent estimate when children are issued to keep consistency?

After creating children, avoid editing the child parts in the parent estimate. Do not change the values of the GLV_ variables as they may be used in the child estimates.

Task Sharing  

Merging back. What is consolidated?

The WBS totals rows show the sum of the partaken items.