Just had a thought about how ML will stay on schedule - acceleration! If both the BNSF and Metrolink locomotives operating in full MU, the train will have about twice the horsepower it normally does (assuming use of BNSF units with around 3K HP) spread over at least twice the normal number of axles (for adhesion). So it might actually get up to the temporary (70) limit more quickly than normal, compensating for the lower limit (instead of 79). Where there are a lot of stations (all but the far ends of the lines), that could help.