Tested in a nightly server (http://nightly2.sakaiproject.org:8087).
When an user copies a pool with subpools, all pools and subpools are copied.
However, if an user copies a pool shared by another user, subpools are not copied.
Steps to reproduce the issue:
1) Login as user1 and create a pool of questions PoolA and a child sub-pool PoolB.
2) Share PoolA with user2.
3) Login as user2 and copy PoolA inside another pool of our own (PoolC)
4) Only PoolA is copied inside PoolC. PoolB is not copied.
If user1 copies PoolA inside another pool, PoolB is also copied, so we understand that this is a bug.