If they're trying to extradite from here, then ALL they need to do is to SAY that they have evidence sufficient to generate "reasonable suspicion" (without presenting it), and in the absence of unusual circumstances (as, fortunately, in this case), that is enough for us to bend over, and take it from behind.
The later Register article has a link to the judgement. Paragraph 9 outlines the evidence which seems to point to there being a prima facie case with some of the evidence coming from the UK police:
In October 2013, the Federal Bureau of Investigation asked the National Crime
Agency [“NCA”] for assistance in its investigation, which led the NCA to begin its
own investigation. Its purpose was to “gather evidence with a view to mounting a
potential prosecution in the UK, whilst being equally aware of the US investigation,
should material relevant to their investigation become apparent....” The investigation
obtained evidence linking Mr Love to the hacking offences. On 25 October 2013, the
NCA executed a search warrant at Mr Love’s parents’ house. He lived there with
them. This is explained in the witness statement of Mr Brown of the NCA dated 29
March 2016, made in connection with proceedings which related to the return of
property taken during the search. One of Mr Love’s computers was logged on to an
online chat room using the nickname “nsh”. A preliminary review of some of his
computers revealed that some of the data stolen during unauthorised access was on his
computers, and these intrusions had been discussed in online chats. Mr Love was
arrested on suspicion for offences under the Computer Misuse Act 1990, made no
comment in interview and was released on bail.
Reading through the rest of the judgement it seems clear that a UK prosecution would be a possibility and this seems to be a factor in the decision. See paragraph 126:
The CPS must now bend its endeavours to his prosecution, with the assistance to be
expected from the authorities in the United States, recognising the gravity of the
allegations in this case, and the harm done to the victims. As we have pointed out, the
CPS did not intervene to say that prosecution in England was inappropriate. If proven,
these are serious offences indeed.
In other words CPS & the US are being told to put up or shut up.