We've uploaded the Expo Authority's document from March of 2007 that verifies that Metro is planning to run the train with 4 minute frequencies in both directions during peak hours. (link) That equals 15 trains per direction, or 30 trains per hour.
On page two of the response to the PUC engineers' protest of the initial crossing designs at Trade Tech, Expo Authority responds:
In case the image isn't working here's what it reads:
"Metro plans to have the following train schedules: 4 minute services for peak periods, 10 minute service for mid-day, and 20 minute services for early morning and night time. Therefore, a total of about 240 trains per day (both directions) will be crossing these eight crossings."
And the actual excerpt from the Expo Authority's crossing application at Farmdale is uploaded, which shows that Expo Authority has applied, and if approved as designed, will get authority to operate trains at 55 mph pass Dorsey HS where over 1800 students walk across in surges daily.