I heard about it before but it does not seem to get much attention. Maybe it is overshadowed by WCT because East Coast Trail is probaby less remote, challenging and wild.
You probably have found its website but I list it here anyway. You can buy maps from them. I also found a few other useful links.
Actually I think it may be a good choice for a casual hiking trip, where we can pack light and go from one B&B to another. It is probably just that there are so many other things to do and places to go in Newfoundland so this trail never gets to the top of people's priority list.