I believe the general grammar for 「ないことはない」 means "can; it is not impossible". However, I am having hard time trying to translate this example sentence:
「どうしても話してくれと言われれば、話さないこともない。」
Mostly I cannot figure out who the subject is. My tentative translation is "You can speak if you are asked to do so." Pretty sure this is not correct and would be grateful for a more accurate translation!
「どうしても話してくれと言われれば、話さないこともない。」
Your TL attempt of that is:
"You can speak if you are asked to do so."
The truth is, however, that the subject throughout the sentence is the unmentioned "I", the first person.
「言われれば」 is in the passive-voice form -- "If I were told", "If I were asked", etc.
The subject of 「話さないこともない」 is also the speaker himself.
Thus, an example TL would look like:
"If I were desperately asked to tell, it would not be impossible for me to tell."
