Hi,
Since HikaShop 2.3.0 we allow to set some email addresses in the $mail variable.
The mail class have this code
		if(!empty($mail->cc_email)) {
			if(!is_array($mail->cc_email))
				$mail->cc_email = explode(',', $mail->cc_email);
			$this->mailer->addCC($mail->cc_email);
		}
		if(!empty($mail->bcc_email)) {
			if(!is_array($mail->bcc_email))
				$mail->bcc_email = explode(',', $mail->bcc_email);
			$this->mailer->addBCC($mail->bcc_email);
		}which is processed just before the email is sent.
For the tests we made during the implementation, we did not find specific issue with that.
But I know that some other mail "gateway" like "mandrill" could not support some features ; like the "addStringAttachment" for example. But I guess that the addCC is implemented !
So using $mail->cc_email and $mail->bcc_email should work.
In some cases, the mailer could be reset between the moment when the email is parsed and the moment the email is sent, so using the $mail object is safer.
Regards,