I'm probably making this much more difficult than it is, I'm also pretty sure that this is answered somewhere but I'm very tired of looking!
This has to do with an ice breaker and encountering a piece of ice. When encountering a piece of ice the first thing that matters is the strength of the two I think. If the strength of the ice breaker doesn't meet or exceed the ice then it is deflected. The sub routines then take effect as I understand it.
If the strength of the icebreaker does meet or exceed the the strength of the ice then the runner must have the correct type of icebreaker to defeat the subroutine or subroutines if there are multiple of the type of ice to avoid those but that doesn't cause the run to fail unless one of the subroutines is end the run. So if I understand a piece of ice that is a barrier can be passed by any icebreaker as long as the strength is high enough. The subroutines can not be bypassed unless the right type of breaker is being used! Am I correct?