I found these tidbits at the link Dan posted:
a prerequisite is that the host supports VST3, AU or AAX instruments
That quote means it will not work in Band-in-a-Box for Windows or RealBand since neither program accepts VST3.
An AU version of EZKeys2 is available so perhaps the plugin will work with Band-in-a-Box for Mac.
the full MIDI content from the legacy version is also included.
In May, all previously released EZkeys titles get converted to EKX expansions. Already own one or a few? Don’t worry, all EZkeys sounds will work in EZkeys 2.