The rights are acquired well in advanced on any technical work. The business folks often simply assume something is available. After all the rights are secured, and it comes time to deliver source to the releasing company ... uh-oh! Where is it?!
Remember, I worked for studios before my medical issues started.
I still remember a property where the only surviving copy was a VHS tape. The film was gone, 1" broadcast masters were gone, and all we had was a VHS tape from the late 1970s. But no ... it gets worse! The owner refused to let us have that tape -- which is somewhat understandable, given how everything else was MIA. But he also refused to do as we asked, and submit a 4:4:4 uncompressed SDI transfer. He wouldn't even do a 4:2:2 losslessly compressed file! What we got a 4:1:1 DV transfer of a VHS tape. The color was absolute $hit, with heavy green shifts that were simply uncorrectable.
And it was a boring.