DCC systems are proprietary. For example, you cannot expand a Digitrax set with Lenz components.
HOWEVER, decoders that meet the NMRA standards (which is virtually all of them) can be used on any DCC system. In fact, some decoder makers do not make DCC systems at all (e.g. TCS. Soundtraxx). They should also be "interoperable" - i.e. even if programmed by one system, they should function on another.
Andrew