Excuse my ignorance but how are they going to do that when calibration should be carried out in an environment with a controlled ambient temperature and humidity?
Site calibration is dodgy at best and feeds off the desperate and impatient.
Unless Yesss are going to set up a restricted, controlled area then I'd steer clear of believing that calibration to be completely accurate.
This is my business, my reputation and my customers lives.
I'll send my equipment off to a reputable calibration company for the 3 - 5 days it takes (usually 3) and pay the £70. It's cheaper than the potential alternative disaster.