Can I use 1 PM866 and 1 PM866A connected in redundant configuration?
From the product guide:
PM861A, PM864A, PM866A are equivalent to PM861, PM864 and PM866 respectively, unless stated otherwise
3BSE076939R1 (PM866AK01), (3BSE050198R1 (PM866K01))
In case you load the same firmware to both CPU's, and proceed with IP config for redundancy pair, it should work.
It would be interesting to know if somebody tried it.