Compatibility with 'SONIC ORIGINS' is there, but there are certain combinations where some save data might not work:
'SONIC ORIGINS' ⇒ 'SONIC ORIGINS Plus': Save data works without any issues.
'SONIC ORIGINS Plus' ⇒ 'SONIC ORIGINS': Data from playing as Knuckles in Emery and Sonic CD cannot be loaded. When starting the title, a warning message will be displayed to install 'SONIC ORIGINS: Expansion Pack' or 'Plus Content Pack.'
Please note that using the affected save data to play the game and saving is still possible.