Yard diagrams are only given to employees as part of the timetable. They are considered sensitive information, so you are VERY unlikely to get current diagrams.
However there is a, now very dated, copy of Pan Am Timetable No.1 on the FRA website, posted as part of their PTC plan proposal if I recall.
It can be viewed here -> http://www.regulations.gov/document?D=F ... -0068-0002" onclick="window.open(this.href);return false;
That link will take you to the page from which the file can be downloaded. Its a .pdf and is viewable with Adobe Reader.