I have a question regarding Eircom's broadband service and the ip address ranges assigned to users from the overall range assigned to Eircom.

Different Eircom users seem to be assigned to different pools of Eircom dynamic ip address ranges.

What determines the range assigned to a user?
Is it based on geographical location (i.e. different areas within Dublin)?
Is it based on the telephone exchange the users line is associated with?
If the users router is switched off for a prolonged period, will a different range be assigned when reconnected?
How can a different pool of dynamic ip addresses (within Eircom's complete range) be acquired?