Hello Darcsypher,
Welcome to the community!
It's always good to be cautious about such advertisements. While I can't say for sure the message you received is legitimate, Fido has offered their customers the same or similar offers (see here, here, here, here....).
If you wish to verify the offer you would need to contact customer service. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above.
Hope this helps 😀
Cheers
