This is a very usual thing to find. With regard to film, people generally don't throw it out when a building gets abandoned because they don't know what to do with it. In this case it's most likely material used for making the films, such as cutting copies and trims. I do hope that there were no cut negs there and I think that highly unlikely. The Shaw business still operates, mostly in property and they probably own this site still, which they shared with TVB. It's a demolition site now, so everything has gone. Shaw still operates as a media organisation and the important stuff is still marketed, so I think this is a case of useless material being abandoned.