There is no set answer unfortunately - each hen is an individual. It depends on how hard their molt was on their body and how much weight they lost during the process. Once they feather back in, they have to get their body weight back up before they can start laying again. When their combs start turning back to a bright red, they are getting close to starting again. Some hens will go through the whole molting process in a couple of months, some take longer. My English Orp usually takes 4-5 months to molt, but she's got a TON of feathers to replace.
I can tell you that it has nothing to do with the molting of others. They start back up when their bodies are ready to.
My cream legbar is finished growing in her feathers, and I can see her putting on weight. She'll be laying again soon.