Ohhhooo...my first post

Well here it is. My company is considering a sublet agreement with another expanding company in our office building.
The other company has outgrown their current space. From my first meeting, the impression I got is that employees [just 5-10] from the other company will be given cubicles in our space with WIFI access to their own network.

My concerns are mostly with accessability of the other employees to our own systems and network.
what would prevent one of the others from walking into one of our own offices after hours etc...and accessing a workstation for example.
Has anyone had a similar situation?
Any suggestions on how I can best raise my concerns to Administration [who is blinded by dollar signs, bonuses and percs and has no clue about possible risks] .

Newly appointed VP actually told me that sometimes dollar signs outweigh the risk.

Can anyone point out other areas of concern that I should address.