For the purposes of clarity, I just had a discussion with the TBC Development Team on the VCL Library use in products like Siteworks. TBC at each release will have a new VCL Library support and it can write out everything that TBC can create and Read it back in again. The VCL Library that is incorporated into the Field Systems to decode and use VCL Data may at times get outdated by a new version of TBC if the Field System is not updated in parallel. However there is a Flagging System in the Field System Library that identifies object types that are not supported with the version of library and those objects will get ignored.
For example, when we added the Extended Sideslope functions to TBC, the VCL library would write those out and read them back in again no problem. If a field system was able to read the corridor models but had an earlier version of the VCL library, those new extended objects would be ignored, so the corridor would have no sideslopes in the field system until such a time that the field system was updated with the latest library and the field tools to leverage those extended object types.
When we look at objects like Alignments, Surfaces, Linework and Points which are primarily the objects in use in the field systems today, they have not changed much if at all over the past so they are unlikely to trip up because of a VCL library change.
Hope that this is helpful information
When I receive your file we can take a look to see what is happening
Alan