Here's my best guess. Given the number of agencies responding to this incident, they probably assigned communications for that incident to one (or more) of the Statewide Interoperability Talkgroups. These are the F TACs, L TACs or E TACs. Or they may have patched in a Hennepin County talkgroup to a state tac talkgroup.
A savvy radio user (police officer or firefighter) from your area, probably tuned his/her radio to the state tac talkgroup to listen in on the incident. When a user selects one of those talkgroups, a link is set up between the site in your area and any other sites where a user has selected the talkgroup. (It's the "magic" of the Minnesota system).
So because an emergency responder in your area was listening to the Rogers incident on a state tac talkgroup he created a link that you were able to "piggy back" on to with your scanner.
Here's kind of an example, the way I understand the system. Let's say a state trooper in Minneapolis is in pursuit. The state patrol dispatchers will patch the state patrol district talkgroup to L TAC 1. (That's so any Minneapolis units which may assist can talk to the trooper). A police officer in Duluth can switch his portable to L TAC 1 and can listen to the pursuit (at least as long as they keep the patch in place).
A similar thing occurred years ago when the 35W bridge collapse occurred in Minneapolis. Several "outstate" users "tuned in" to the talkgroups being used. There was (and may still be) a report describing this on the state radio board site. The downside of this is that it ties up a voice channel for the "outstate" areas, reducing voice channels available for use in the given "outstate" area.
This is a pretty technical thing and trying to explain it simply can be a challenge. Hopefully I've helped you make heads or tails of this.
