No, technically you should use "siate" (Siate pronti a tirare). Actually, the imperative form of "essere" is rarely used, because it sounds archaic. You can use it in wishes like "Sii felice" (be happy), but that would sound a bit rethorical.
To fix this, you can replace "essere" with "stare": "state pronti a tirare" is the standard way to translate "Be ready to pull".
Of course this applies only to "siate" as an imperative and has nothing to do with "siate" as a subjunctive form.
The meanings of tirare vary molto molto with the context. I doubt if many Italians could list them all from memory. https://dizionari.repubblica.it/Italiano-Inglese/T/tirare.html
If you think that's bad, stay away from fare. Except one can't.