Are all SCADA systems OPC UA based?

Just wonder if all scada systems are OPC UA based to provide the access to the tags?
In particular i would like to compare:
1 - rockwell factory talk site edition
2 - citec scada
3 - iconics
4 - intouch
6 - ignition - this is OPC UA for sure
7 - wincc

How did tag servers work in the past ? was is DDE...?
Please share your understanding if you can
No, not everything is OPC UA. I know of two places using a version of iFix that is still running OPC DA V2 because the mandatory Microsoft update for the DCOM security component is approaching in March.