If you delete the file from your server it wont be accessible on your server anymore, however because I uploaded it to mine it will still be accessible if people load it from cdn.hzrd149.com

similar to nostr relays, blossom servers aren't aware of other servers and don't have any p2p communication.
however there is nothing stopping them from talking p2p, but that code (and protocol) hasn't been written yet

But we don't necessarily need p2p communication for censorship resistance. user can publish a k:10063 event that advertises where other users can easily find your blobs.
So if you find that one server has gone down or is censoring you. you can transfer or re-upload your blobs to a new server, then update your k:10063 event to let other users you have moved
https://github.com/hzrd149/blossom/blob/master/Nostr.md#user-server-discovery