"I do not think he has been prepared for that."
Translation:Je ne pense pas qu'il ait été préparé à cela.
I agree it is a little odd but I think it makes sense in english if you think of it in terms of someone like a teacher or coach who should have prepared someone for an event and has failed to do so. However, my problem is that I don't get why we have a subjunctive of avoir in the present followed by two past participles. I accept that I'm rubbish at the subjunctive but I just don't get it. Also why not pour cela rather than à cela? Can anyone help?
It is passive in French, so it has to be passive in English as well, because this clearly involves a third party, and the tense in both languages (passé composé/present perfect) expresses that the action started in the past and still has an influence in present (like: until now/so far).
Alternatively, you may consider the action as past and complete and translate "qu'il ait été préparé à cela" to "he was prepared for that".
I did not think he had been prepared for that =
- Je n'ai pas pensé / Je ne pensais pas qu'il eût été préparé pour/à ça (plus que parfait du subjonctif, passif).
However, since nobody uses the subjunctive imperfect or pluperfect nowadays, you would use the past subjunctive, passive instead: qu'il ait été préparé