Wow talk about Deja Vu! I signed up just to answer this question. We had the same arguement with our counsel and the ISP who ran the DC. The ISP explained we are not leasing the space they are just allowing us to house x amounts of rack space within their racks. period end of story. The only other privileges we have are being able to run more data or phone lines to the unit.
Anything else is going to be a no-no with any normal ISP. If it is just a co-lo run by some local people you might be able to get away with it. But then would you want to leave THEM with your equipment?
I think not! Good Luck!