CBC story on the project and the EIA this morning.
https://www.cbc.ca/news/canada/new-brunswick/saint-john-data-centre-9.7167767
Sounds like the water concerns are a non starter which leaves the power plant emissions for the opponents to hang their hat on.
My first thought is that growth and development doesn't come without change and not all of it is going to be positive. This is one of those situations where a value judgement has to be made at to whether or not it's worth it.
One thing that does come to mind is that given NB Power's application for a gas plant along with Voltagrid's means the emissions for the data centre will be 400Mw of gas fired generation.