I used flew EWR-SAN and got the 50% e-ticket bonus and just booked a EWR-STL flight and got one. I've asked CO's elite folks several times about this and always get the same basic answer.

"We offer it on some fare's and some flights"

I'm trying to find of where and when, but either CO's agents don't know or won't tell"

I must admit it made the EWR-SAN flight a onepass bonanza.

Fare was $307 roundtrip and the onepass miles added as follows:

Actual 5436
Gold elite bonus 6795
e-ticket bonus 2718
credit card miles 307

and for the really GRAND total

15256

Now you see why I'm trying to find out where and when this is offered