I've wanted to do similar, but unfortunately, depending on what your Fioptics installation looks like and how it is provisioned, the option to connect a cable-ready TV or any other QAM tuner directly may not even be available. See this post
for some info on my installation.
In short, mine is FTTH with IPTV, and as such, there is no RF signal anywhere in the entire setup. If yours looks like this, then that would explain why there are no channels showing up when you scan. I talked to Bell about this, and even pointed them to their own FAQ page that clearly states that you can tune basic channels without a STB, but was told that new installations (at least new FTTH/FTTP installations) would be strictly IPTV.
I have been successful at getting the unencrypted multicast streams setup in MythTV, and I can have up to 3 of those recording at once without any issue. More than 3, and they all start coming up completely garbled, but this is a limitation of my internal network's hardware (an old router that doesn't handle multicast traffic properly...)