I can't say yes or no for sure but I think it would be very beneficial to do during a juice fast and would help alot. You will be detoxing heavily and OPing will probably help your organs cope with the release and overload of all the toxins you have stored up. By pulling them out during the OP your organs will get a little rest and won't have to deal with as many toxins.
I would also make sure that you do an enema atleast every other day (if not daily) to help your colon eliminate the toxins...if you are not doing that already. Since you are not consuming solid food there isn't anything to really push the waste out. You definitely don't want all those toxins that are stored in your colon to be readmitted into your body. A colonic would probably be excellent at this time and way better then an enema if you could do it.
Herbal teas are also great during a juice fast and will help your organs to release toxins. Chamomile is fantastic and very calming, Detox tea is great for the liver as is dandelion tea. Get Regular teas are also great for the colon.
Okay, I will stop going on and on...I gave you way more then you ask for, huh? Hope it helps :)