Some of you posters are getting too complicated. It's really just this simple.
- Job order come in to Company B install new service
- The technician installs their equipment to existing cable
- Old service is knocked out
- Service call is placed Company A to fix outage
- Company A connects the back to their equipment
No one knows, cares or is informed that there is existing service that needs to stay.
It doesn't matter how many DIFFERENT services providers one single dwelling can have. Multiple accounts from the SAME provider could be an issue, but that's not the case here.