This isn't news - in England at least it's been mooted here for a long while.
These powers were introduced into a number of local Council's "safer neighbourhoods" schemes under the guise of reducing 'anti-social behaviour'. Such schemes make extensive use of PCSOs and Specials, as well as a team of regular Police officers. They are however deemed 'voluntary partnerships' - except for many of those they 'target', of course.
Existing legislation permits stop and search for 'cause' - it has done for years but to nobody's surprise it is widely abused. This latest planned encroachment merely rubber stamps what is (to many), de facto existing practice. It harks back to the 'Sus' laws of the 70s and 80s - which themselves were, if I recall correctly, rooted in a vagrancy Act dating back to the early 1820s.
Sus laws were a disaster, and set back race (and Police) relations back years. While I hold the Police (and this Government) accountable for the abuse of such powers, ultimately the root cause is human predjudice - i.e us. Today, while we have replaced racial tension with terrorism as the primary motivator for enforcement, the underlying predjudice remains.
If such powers are (re)introduced, then like the flip flop fiasco that is a proposed mandatory ID card, it will achieve little or nothing positive, almost certainly quite the reverse. It almost certainly won't reduce or avert terrorism (as above, the current catalyst for such powers) other than through blind luck, hardly an effective strategy.