I work in a predominantly Scrum division with rigidly set iteration lengths (technically not scrum as this should be decided by each team, I know). It is horrible, so much wasted time trying to play by the book on this.

Every once and a while we have to break out special teams for a cross group project, a special POC, or something super important with a tight deadline. In those cases the team becomes much more engineer led than management led and in most cases we revert immediately to Kanban style. Not surprisingly for me, we always get more done in a faster manner with Kanban.

Things get done when they're done, not when an arbitrary sprint end day has occurred. Kanban allows you to move work along as needed and instead of focusing on meeting that arbitrary end day, we all get to focus on continuously getting stories closed out. All we needed for this was a kanban board in whatever tracking system we were using at that time along with a reliable form of communication between team members.