I have some Employee Timetable reprints from CRM that date from the late teens and early 20's. They show a "scheduled" freight each way (at night). I would venture a guess that scheduled freights disappeared in the early 20's.
In some timetables from the 40's there is a mention in the special instructions about carrying passengers on freight trains and that those trains ran certain days (like Mon Wed Fri) leaving at "about 11am". and that cabooses would not stop at depot platforms for boarding. So I guess at that time there were "kinda-sorta" scheduled freights.
As no freight schedules were shown in the employee timetables, they all ran as "Extras".