No I don't think its necessarily because of the 4G rollout.
My iPhone5 has a Orange/EE 3G sim card and contract.
This is what my theory is...
My iPhone5 is set to automatically select the best network. It can see the 4G EE network is available, but when it connects via my 3G sim card it glitches / nullifies the signal and just reports that weird 000-00.
Ever since I turned off 4G / LTE in settings I have not had the 000-00 error.
So now it isn't getting confused with 4G and 3G signals, it doesn't give the error.
So my theory is supported by my experience.
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Out of curiosity, is everyone who is having this problem absoloutely sure they have 4G sims??? I got my iPhone on release day, as a new contract, assumed it was 4G and only found out after a customer service phonecall much later that infact the new contract I had taken out was only a 3G one despite it being a brand new contract with an iPhone5 (yet that was one of the selling points by Orange / EE.)