Those numbers tell me that the mic has a DC input impedance of 60K. If you have the 48V rail connected directly to the 6.81K resistors, ohms law tells me that you should read about 43V at the XLR pin2 (or 3) to ground with the U87 connected.
If I'm missing something here, I'm sure someone with a bigger brain will jump in and correct me.
Cheers
Mike