Hello Drago Trebeznik, the DESFire family supports multi application, with this you can set up different keys for different applications so if the same tag is used by different service providers one can no delete the other, you can set up if one key can delete, write or read etc.
please check the tips and hints document to se examples also please check the datasheet to inquire more in the world of DESFire, if you have more questions please let me know.
Have a great day !