I think I agree on the 1978 date for the switch to run via Schenectady. The same post gives a date of 1/12/1986 for the switch from NJ/CP to CN north of Rouses point, which seems about right considering other things that were going on at the time. The link was corrupted, here's a good version:
http://cs.trains.com/trn/f/507/p/44882/1242792.aspx" onclick="window.open(this.href);return false;
http://cs.trains.com/trn/f/507/p/44882/1242792.aspx" onclick="window.open(this.href);return false;