No. You actually got 2 no's on this one.

1. You cannot standby out of a different airport. There is a common misconception that a "co-terminal" allows standby. It does not. You can get some sort of accommodation in irregular ops, but that's about it.

2. You cannot standby for a codeshare partner that is different from the one on your ticket. Reason for that is revenue. The bulk revenue goes to the operating carrier, and all though CO and NW are "partners" they are also competitors, so taking your CO ticket to NW would actually cost CO money. The only way to do what you describe would be to change your ticket.