The tip of an ignitor plug would just sit inside the combustion zone, perhaps as little as 2mm, more and its tip would fast erode, too shallow a penetration = wet starts. Not knowing the P&W but the tertiary airflow around the combustion casing would be at HPC temperature, high enough to cause a fire sensor trip, but flames escaping the inner combustion zone I do doubt very much, as the airflow pattern is designed to keep the flame from touching the sides which in any case would have several rows of holes/scoops to allow the tertiary air to dilute the flame for introduction into the HPTV's.