First of all - TYROS OS is Flash ROM Based.

It is of course planned to do some kind of bugfix if neccessary. You have to use a PC with USB connection and a program for the update procedure. This program is a small application and puts the huge amount of data into the TYROS. This is not difficult but takes app. 30 minutes. IF something happens like a power failure or disconnection of the data cable you can't revive the instrument easyly.
This is why Yamaha doesn't want to distribute the data to everyone.
Of course you can order the data if it's available and do the update procedure. But you have to be sure to have the technical talent. Otherwise you can contact your local dealer or service station.