It's for sure a technology which is mature enough that it should be deployed, even if in trial batches. Just note that it's not going to perfect policing.
Their reasoning boils down to the fact that it's not perfect and it's not proven, therefore it shouldn't be used until it is.
A representative from the ICCL was giving interviews yesterday and he came off as a little more reasonable than the press release. But as far as I can tell their big bugbear is mass surveillance. Which is a good thing to oppose. But they're completely blinkered by the issue so will oppose anything which might increase the number of cameras in public places. If they took more of a "maybe, if" stance rather than "no no no", they might get better traction.
A member from the GRA pointed out that body cams would be of massive benefit in domestic violence cases where a victim is often reluctant to give a statement after the fact. Body cam footage would give the Gardai the ability to pursue prosecutions without the victim's cooperation.
The ICCL guy had no real respone for that except to go on about data and unproven, etc again.