There is a sure-fire way of opening any links in a new tab;
hold the left-shift key while left-clicking the link
This works in all the browsers I'm using (IE, FF, GC, Safari).
I think the middle-click opening in a new tab is probably the mouse driver on your work mouse and it won't be standard on all mouse drivers.
The tip above is built into Windows and should interpret through any browser (if the browser support tabs).