Only devices with the same firmware grade can be added to a network of the same type (i.e. Classic devices can only be added to a Classic network; Evolution devices can only be added to an Evolution network).
If you have a network with different grade than the Casambi units' firmware then you will be prompted to update the firmware of the unit in order to add it to the network. If it is not possible to change the firmware (due to the device using an older processor) you will not even be prompted with the option to update the firmware.
NOTE: Only devices which display as Classic or Evolution within the NEARBY DEVICES list can be updated to Evolution and used within an Evolution network. For specific Casambi products which can be updated to 'Evolution' firmware grade here: http://support.casambi.com/support/solutions/articles/12000058791-which-casambi-products-can-be-updated-to-evolution-firmware-