The company need to explain why the restructuring means that the request cannot be accommodated, so yes the employee can ask for further information. Whether they will receive it or not is another matter.

In reply to Elizabeth:

It is the most vague of the 8 reasons.

If it means that W we will be announcing a reorganisation very shortly so hand on a bit then it makes sense
if it means we do not have to explain then it will be open to challenge