You're obviosly unaware of the acl_xattr module shipped in modern Samba, and used by most OEMs.
This stores "pristine" Windows ACLs in an EA on the filesystem, and consults them before allowing access to the underlying file/directory. The mapping to underlying POSIX ACLs (for systems that don't support them) is done underneath this layer for compatibility with NFSv3 and system process accessing the same files.
Samba of course has a full mapping into NFSv4 (ZFS, or GPFS) ACLs, which will be supported on Linux once the "RichACLs" patch is accepted into the kernel.
So yes, ACLs *do* work in the general case in Samba, and many successful OEMs ship with them turned on.