Only if they're the same version (which using the older built-in package system all packages are likely built against the same version)...
If the containerised versions of apps all have different versions of dependencies (quite likely IMO as they'll have the freedom to), there won't be any sharing.
Or even different locations. (unless they're hardlinks, or COW files probably) If it's not the same block on the disk, it's going to be duplicated in cache - whether it's the same contents or not.
If the containerised versions of apps all have different versions of dependencies (quite likely IMO as they'll have the freedom to), there won't be any sharing.