I see a few problems.
Firstly, they plan on releasing *some* of the data, but that will lead to cherry picking, with the spooks choosing the recordings that back their case. The defence should be allowed the same access to all the recordings of that person.
All, because the person was there, so you are not telling him anything he doesn't already know. And others know when they spoke to the target, so they know too. All parties in a conversation know about the conversation!
All, because a 500GB portable hard disk can hold a lifetimes worth of voice recordings, so it's not difficult to give them a copy.
All, because voice recording equipment keeps the spooks comment, target id, channel etc. in a database with the recording. It's very trivial to give them a copy of all the voice recordings they have that include that person. I don't believe that the spooks have substandard interception equipment that doesn't meet evidence gathering standards, but yet the police do? Pull the other one it's got ringtones on it.
BTW, if you want to learn about pro voice interception/recording equipment grab the brochure.
The defence should be able to transcribe the parts that show their defence case as much as the prosecution can to prosecute them.
Look at it this way, you go to court, "Ivan said death to Blair in this recording here", perhaps he also said "You know, I often curse that Tony Blair but actually I'm his biggest fan and I'm just joking around" 500 times. To present only the "death to Blair" text out of context like that would be misleading.
As for the 'we have special tricks that would be revealed'. It's done in mainland Europe and I don't believe that there are tricks only known to the UK. That master class he theorises about would have already happened in mainland European cases.
IMHO, They should also remove control orders and the like. Anything where a spook, based on a secret interception, whispers in the Home Secretary's ear and he in turn imposes house arrest based on this unsound unchallengeable information. That should end, they do house arrest under political order in Burma, it has no place in the UK.
Put it another way, if the evidence wasn't sound, they'd go whisper in Home Sec's ear, but then unsound evidence is the type the court is there to protect against! It's the iffy times you exactly want the court to examine.
Likewise all the other flows of information to government departments which in turn lead to plastic police investigations. i.e. pseudo police forces in each government department that investigate stuff directly instead of asking the police to do it. Surely it's a police job?
"An example of the operational constraints this can impose can be found in the operations of bomb-disposal robots."
If BBC made a TV program "Bomb disposal, heroes on the extreme edge", they'd be lining up with their bomb disposal videos.
You can't both argue that
* Terrorist are getting off free because we can't submit the evidence
* We can't submit it because we need to protect our bomb disposal techniques.
Are the bomb disposal techniques so important that it's better to let terrorist go?
If you can't convince a judge it's so secret it should be kept from the defence then it shouldn't be, because the judge is the independent viewpoint.
We should get back to that system, where the police investigate, the judiciary prosecute, the government legislates. No more plastic police, taking on pseudo police roles, no more politico taking on judicial roles, no more vague legislation that leaves the fine detail up to the police.