I think it's in the Psionics chapter of the core rulebook or a nother chapter on psi-tech, where it's mentioned that official diplomats are allowed to use psi-shields when operating in the Consulate. But other people need permits from the Zhodani government. Now, since corruption seems rather low in the ZC for reasons of re-education camps and psionic control, obtaining a permit through the black market might be highly unlikely. Corruption here being unlawful bending of the rules by proles, such behaviour by Zhodani psions who can shield themselves is another matter entirely. But back-channeling these permits from nobles or faking them. However faking theses permits will only be feasible, if in general 3I computer technology has an edge over ZC technology in that regard.
So, if I were the Imperium, I would keep a token force of psionics for defence research and shielding high-value targets, and also try to keep a general edge in my TL over the ZC. This would also allow for other means of espionage against the ZC. And I think these means would likely yield more results, namels SIGINT in general, OSINT and other tech-based intelligence gathering forms such as digital network intelligence, financial intelligence and technical intelligence.