I understand there is a trial being conducted at the moment on an extended protocol for TMOs in rugby union: "TMOs are currently only involved in plays involving tries but may be asked to rule on possible foul play as well as reviewing up to two phases before the ball is grounded for a try in both domestic and international matches." (Newspaper report in January this year). The wording "rule on" is very vague, so it doesn't tell us much about how it would operate. However, the news item confirms my belief that currently the use of the system in rugby union is extremely limited and involves only validation of a try.
