/-----------\             /-------------------\
 |  Company  |--@(has-N)-> | Company::Division |
 \-----------/             \-------------------/
      /|\                          /|\
       |                            | (is-a)
       |                            |
       |                   /- - - - - - - - - -\
       | (is-a)             AcmeLtd::Division ?
       |                   \- - - - - - - - - -/
       |                           /|\
       |                            | (is-a)
       |                            |
 /-----------\               /-------------\
 |  AcmeLtd  |-----create--> | AcmeLtd::IT |
 \-----------/               \-------------/
[download]

A company may have more than one division, and the number may change over time, but the distinction between them doesn't really matter. So consider a collection of generic divisions.

In the AcmeLtd construction, or later in its operation, you may choose to add an AcmeLtd::IT instance to the collection of generic divisions of the company. You may choose to nix it later, or outsource it to some Vendor::IT that has a similar interface.

If there's nothing particularly distinguishing about all AcmeLtd::Divisions that would not be required of any generic Company::Division, then kill that class.

(ASCII is not a very good way to draw Booch diagrams.)