"That (to me) is sufficiently unambiguous to convict them." IAAL, and I can see ambiguity here, though you are riht in implying that there is a prima facie case to answer. First of all there is the intention bit - whilst it may be in the letter of the law, simply seeing SSIDs and recording them may not be within the spitit of the law (for instance, I can see several on my laptop at this moment). Even regarding the extra packets, there is a big enough question as to whether *Google as a company* had the intention that a half-decent barrister could get them off.
Secondly, there is the disclosure element. Google has not disclosed anything unless ordered to by a body with the appropriate powers. Yes, there is a question as to what they might have done with it in the future, but as it stands, no offence has been committed regarding disclosure.
Finally, and I still cannot work this out, how can it be illegal to intercept a radio signal in clear which, in some way, gives location? I'll use the example I've been using all the way through on this topic. I am using my PMR radios on a given channel in a place where I know others will be using PMRs, and I hear someone else (not a person I am intending to have a conversation with) come on the same channel and say (to someone not connected with me), "Hi, its Steve, I'm over by the monument". If I am within sight of the monument and I look over to see one person stood there, I know that is Steve. That satisfies s48(a). If I then say to the person next to me "That must be Steve there", I have satisfied s48(b). This is what I regard Google as having done, and I think this is a hurdle that any prosecution must overcome - the radio landscape has changed since the WTA2006 was drafted, and far more people have unlicensed radio transmitters than before. This means that there needs to be an element of reasonableness in the whole thing - i.e. was it reasonable that I (in my example) or Google (in reality) picked up unlicensed radio transmissions sent in clear without going to abnormal lengths to do so?
Whatever happens, lots of lawyers are going to become rich off this case. Any prosecution is going to go all the way to the Supreme Court (it still seems wrong not to write "House of Lords"!) on these and many other points if Google is found guilty at first instance.