We do the same as a few CS1000E going in general for sig servers and callservers we just remove the compact flash and hard disks and drill them
MGC I do these
leaveSecDomain
mgcIPClear
diskFormat
with the call servers you can drop in a default db but need to remember there are a lot more this in there, like all the node details for example, which is why we figured physical destruction was the way forward. You can use the install disk and the tools menu to format the flash but tbh whats the point, like you say you dont know where its going. If some one really want to reuse the devices they can source their own media.