I2C bus through bricktronics shield

Hi,
I am a new owner of tHe UNO-type bricktronics shield -rather satisfied so far.
I would like to operate NXT motors according to heading and tilt indications coming from a LSM303DHLC compass+accelerometer sensor.
From a first test, it appears that the bricktronics shield does not allow communication of external sensors wired to the IC2 SDA SLC pins (or I missed something …)
What about connecting this LSM sensor to one of the sensor ports of the bricktronics and using the ad hoc library ?
Thank for your help

Frank