Yeah, it absolutely happened. I don't think they ever paid for private certificates. But there was a full page advertisement in Plane and Pilot magazine back in the 60s where United was advertising to pay for commercial certificates (250 hrs.) and get a job with United. In other words their hiring minimums were a private certificate and instrument rating.

I remember seeing the ad recently that somebody scanned and uploaded to some other forum or group. Wish I could find it.