Whiile one can’t be certain of anything, it is interesting to look at the claims of the UK sailors and marines released from Iran, and the Iranian released from Iraq.
The NZ Herald has a story on these.
I note the British claims are very detailed and precise. They talk about actual incidents, timings etc.
While the Iranian released from Iraq just makes the claims that he was “Tortured day and night” and that “When they were faced with my answers about the official relationship of Iran with the Iraqi Government and officials, they increased the tortures.”
Now regardless of what you think about the probability of each country to undertake certain activities, the Iranian’s claims sound very contrived “I was tortured day and night” and “They increased the torture” are somewhat lacking in details.
No way to know for sure, but I am sceptical. They really should train people up to lie better.