Hi Anthony,

In addition to matt's comment, you might consider:

1) create a hard table in an external schema or schema defined through a custom module. these tables can be shared across containers.

2) if you could use an assay, that assay could be defined at the project level or in /shared, in which case it will be visible to subfolders.

depending on your application, you might also be able to to have a single list located in 1 container, then view/insert records into this list from both containers (see containerPath on most APIs and the QueryWebpart).