UEPEO
UNION ELEC CO 4.50 PR
stockOTCPreferred Stock

I used to own an electric company a long time ago, Union Electric Company. It was previously traded on the NYSE and it was merged or acquired by another company Ameren I think around 2007. Now, Union Electric is a subsidiary of this company but is traded on pink sheets despite being profitable and being worth $7B. I don't quite understand this. $UEPEO [https://en.wikipedia.org/wiki/Union\_Electric\_Company](https://en.wikipedia.org/wiki/Union_Electric_Company) In my experience if it is a cash offer or merger the shareholders approve it, cash is paid to existing shareholders or shares are changed to the new ticker and the old ticker disappears. Why would a company still list the shares as pink sheet stock after the deal?