Just a second ago at school I suddenly had this thought...
SPOILER
You remember when you blow up the teleporter that Breen is in near the end.
Well you also remember that you took a week to teleport from Nova Prospect well what if Dr Breen was teleported a few years forward or maybe backwards.
I noticed how the Gman has a similar head structure... Why would the Gman send you to this era. Perhaps Dr Breen is very close indeed as another person from say the past or future.
Try and guess who I am talking about...