I thought that when booking via a corporate TA they have to be the main contact as they own the booking and they need to know of any schedule changes or cancellations so they can deal with as per BA travel trade rules.

Even if you got notification of cancellation you’d need to get the TA to deal with it and if they’ve not been informed it will take longer so I think the solution is TA stays as main contact and you are copied on all changes.