Here's my method of automating Bachmann Blue Riband couplings, hope it may be of interest.
Basically, it uses re-shaped steel office staples and pairs of magnets buried under the track. The staple tails are attracted down by the magnets, causing the hooks to rise, but only when the hooks are unlocked (i.e. slack). By all means try the idea yourself.
Cheers, Brian.

Two vans coupled to the left, buried magnets located as shown. Two spare magnets in front to show size.

The two vans coupled in tension over the magnets, remain coupled.

The train reverses slightly, unlocking the couplings, the hooks rise.

One van is drawn away to the left.

To recouple, the vans are pushed backwards over and away from the magnets, they recouple.

Plain ballasted track, magnets not visible.
