The police? This is a political move. The police don’t have the equipment to detect spy equipment. The way to do it is to set up a broad range antenna and scan the spectrum while focusing on likely targets. Likely targets are windows and plastic or fiberglass domes on the roofs. It is unlikely an embassy would have such radiating equipment because it needs to be in a location where it can hit a target of interest.
More likely, satellite phone emissions and transfer towers would be targeted. They might bounce microwaves or lasers off individual windows, but that wouldn’t be done from an embasy. They need plausible deniability.
Spying as suggested in the article is extremely unlikely.
Yes, we're spying on you and we use our embassies and consulates to do it, just like every other first-world country does to every other other first-world country.
There. Ya happy?!?