I'm trying to determine how much monthy bandwidth we will need, and how much server we will need. I assume that we will at least need a dedicated colocated server, but will that be enough or will we need a cluster? Who are other people using as hosts?
The channels that are published publicly, what is the range of montly bandwidth that they require?
The amount of streaming really varies widely depending on the channel and content. Many channels use one of the Online Video Platforms (OVPs) to manage workflow, syndication and distribution rather than maintaining their own servers. There are any number of these out there including (in no particular order) Ooyala, Unicorn Media, The Platform, CastFire, BrightCove and Sync.tv.