for all things Athletics, that is World Athletics. They have points tables they use for world rankings. By looking at the tables you can extrapolate what they feel they the conversion is for 200m indoor track vs a 400m outdoor track.

For example a 4:19 indoor mile on a 200m track scores 898 pnts, in order to score 898 pnts outdoor you would have to run 4:15. So there is your answer - according to World Athletics its 4 seconds for a mile when in the range of a 4:15-4:20 mile.

You can use this app to easily convert time instead of going to the tables to figure out other times and distances. Be warned you have to use mile and two mile as world athletics does not recognise 1600 and 3200m.