Charged with planning it, it's call conspiracy. They likely were just BSing and the mole turned them in.
Conspiracy is what they charge you with for talking about something. Sometimes the judge will insist those charged actually do something. Like buying blakc powder and/or plumbing supplies.
It’s not just planning. Conspiracy is an agreement among two or more persons to commit an unlawful act, and it requires that at least one of the conspirators commit an overt act to effect the object of the conspiracy.
It will be very interesting to know who was the mole/agent provacateur in that group, and how much of the “crimes” were his instigation.