N
I spoke too soon! >.<
From a fresh wipe and firmware upgrade, I was able to run the I2C library. However, once I loaded my own modules onto the device and used them to connect to my network, calling "init" on an I2C instance caused the WiPy to freeze (connected over serial, but I could no longer type into the console).
I built a bit-banged version of I2C yesterday and am able to use it on the same pins ("P8", "P9") without issue.