A/T disconnects during TO roll are rather common on the CSeries during (gusty) crosswind conditions. This is due to the A/T application only using a single airspeed source whereas the monitoring function uses a consolidated value. If they disagree too much, it will disconnect.
As already mentioned the buttons look and feel the same and are positioned just next to each other on the flight control panel. There were several cases (obviously in different companies) where crews tried to reengage the A/T, few of them pushed the AP button, which will eventually command up to full up elevator deflection.
For me these events are a combination of poor system design (IMHO the A/T generally is a mess on this plane) and pilot training (why should one attempt some button pushing on the FCP during takeoff roll?! there are thrust levers for a reason...), but I am quite surprised the authorities are only picking up now on these incidents, being familiar myself with them since more than 2.5 years.