The question of MSEO Encryption and decryption

Hi all,

I have a problem about the MSEO(media server encryption option).

backup environment like below：

DC SITE(MAST BACKUP SITE)

Master server: SHAA2SNBU38

Media server: SHAA2SNBU38

first backup data to DD640,then vault to tape in i500.

DR SITE(DISASTER RECOVERY SITE)

Master server: SHAA2SNBU38(the same DC site master server)

Media server: SHAA5SNBU61

backup type like DC SITE

Now i have problem:

Vault to tape is through encryption by mseo(media server of SHAA2SNBU38).Then i take the tape to DR site and recovery the tape from media server(SHAA5SNBU61) successfully.But the site of DR(SHAA5SNBU61) is out of mseo agent. why it does sucessfully?

additional query:Recovery data what backup through MSEO must need media server installing MSEO agent?