bmster, you've got it mostly wrong.
Rogers bought Fido and created Chatr as a fighter brand, has nationwide 2G GSM on 850/1900, 3G UMTS in some cities on 850/1900 and 4G LTE on 1700 in Toronto (I don't think they've launched anywhere else yet)
Telus bought MiKE and created Koodo to compete with Fido and Virgin. Telus and Koodo have Nationwide CDMA on 800/1900 and 3G UMTS on 850/1900 (incidentally, 800 and 850 are the same, just for some reason with GSM/UMTS it gets called 850). MiKE is on iDEN at 800.
Bell bought the remaining control in Virgin, and had bought out and revived Solo to fight Virgin and Fido and has been repurposed as a fighter brand several times. Bell, Virgin and Solo are all on 800/1900 CDMA and 850/1900 3G UMTS.
Bell and Telus are seperate entities, they just have tower sharing agreements with Telus using Bell's towers in the East and Bell using Telus' towers in the West.
There are also a number of MVNOs, like DCI Wireless (which is probably mostly dead now, but was a Fido MVNO before they were bought out by Rogers, and kept the same deal without renegotiating), Ztar (which rebrands as 7-Eleven SpeakOut and Petro Canada Mobility) which buys from Rogers, and Presidents Choice Mobility which buys from Bell. The only Telus MVNO I'm aware of was Amp'd, and that's been dead for ages.
At the moment, pretty much every carrier and MVNO (probably excepting DCI) except for Wind and Mobilicity work with GSM phones with UMTS 850/1900.
The word 'Pentaband' means '5 Bands', from the Greek word 'pente' meaning '5'. For a phone to be pentaband it has to support 5 bands. If the phone has AWS support, it doesn't automatically mean that it is pentaband. The reason Wind and Mobilicity users like pentaband phones is because the reverse is true. We're not the only ones who like pentaband phones though, so please stop referring to phones that work on Wind and Mobilicity as pentaband. It causes unnecessary cofusion.