I have a document referring to aircraft with maximum takeoff weight of 45000T. Is this an error?
It stands for metric tons, as indicated in the "GEN 2.1 Measuring system, aircraft markings, holidays" section of the AIP that you linked to as one of the units for mass. 

That being said, the number format appears to be wrong and they most likely intended 45.000 metric tons, which works out to about 99,000 lbs. and is a somewhat common point to use for aircraft classification in other countries.