Right, but the proposal isn't to build a pulp mill but to build a station for transit. These two things serve very different purposes. Being a NIMBY against an industrial mill isn't equivalent to being a NIMBY for a train station that may bring 1000+ new homes or residents or whatever.
As for the VIA stations between Ottawa and Montreal, Casselman is already seeing new suburb growth in the NW part of that town, although I doubt much of that commuting is being done by train and is probably being completed by car. Alexandria has not seen the same development growth because it doesn't make much sense for Ottawa (distance) and for Montreal.
Ottawa has enough suburban sprawl as it is and certainly doesn't need any more. Obviously it would be great if Tremblay could be use for the new HFR/HSR line but it would be typical Ottawa if they ended up with a new greenbelt station in Greenboro or wherever else.