A phone holds a logo for every known network it can be used on
If you have a data cable this can be changed but you will only change the logo for the network you are on, there are two ways of demonstrating this.
1) Send yourself a new logo and then change sim cards to another provider, you will see your logo has dissapeared and the other providers logo appears e.g. you picture when you had a cellnet (o2) card in has dissapeared and it now displays UK Vodafone.
If you then put your cellnet card back in winnie the pooh will return, the logo was there all the time but the sim card tells the phone which it should use
2) Using a datacable and Logomanager with a nokia phone you can select your network and view the logo for each different provider.
As described before, it is possible for O2 to send everyone the new logo but the time spent and the cost to do this will be futile when a lot of the phones won't be able to accept the logo anyway, besides how long have you kept a mobile phone, most people replace it fo a newer model every year which from now will have the new logo as default
Shaun