Hi,
Currently any data from the "About" roll-out aren't accessible by maxscript (like the installed version) and your solution by using getFileVersion("$max/plugins/ForestPackPro.dlo") / getFileVersion("$max/plugins/RailClonePro.dlo") should be working fine for these purposes (the .savedVersion (.savedVersion & .createdVersion in case of RailClone) properties are meant for slightly different tasks).
Best regards,