Why would the registration number (if regionalised) be hard coded into the phone rather than provided in firmware/software? Because at time of iTunes activation it should know that I am 1) in New Zealand and 2) using a Vodafone NZ SIM card.
It could be, that the carrier bundle on your device, has the entry:
<key>PhoneNumberRegistrationGatewayAddress</key>
<string>00447786205094</string>
Which might explain that 0044 registration number.