An eagle-eyed reader of this blog has spotted the schedules for what we suspect are 350/4 test runs:
5T72 10.40 Crewe Carriage Sidings LNWR to Carnforth Down & Up Goods Loop
5T73 13.03 Carnforth Down & Up Goods Loop to Crewe Carriage Sidings LNWR
The times are different on Mondays and later in November, see realtimetrains.co.uk for details.
Today's runs were cancelled.
UPDATE: The test trains ran on Thursday and Friday, here's a shot kindly supplied by David Hull of the Friday run at Wigan.