I dont think the content can be accessed by mega without the full URL. The URL probably contains the information about the location of the data plus a passphras

I dont think the content can be accessed by mega without the full URL. The URL probably contains the information about the location of the data plus a passphrase to unlock the key to decrypt the data. In this way mega could hold the data without knowing the URL to access and decrypt it. The full URL would only be retrievable through the user interface, which mega would not have access to unless their servers are storing your login password. Which I assume they are not for legal reasons. I am making assumptions here.