>>5896944Phytoestrogens will compete with 17b Estradiol on hormone receptors in the body. Phytoestrogens have been known to cause similar effects as estrogen, but overall they're weaker. Some people have attempted to use them as a replacement for HRT in the past, but it's marginally effective at best.
As for combined HRT and galactagogue studies? I don't think there are any. My doctor who is pretty well informed on trans issues was curious if lactation was a possibility when I asked her about it - she didn't seem to be under the impression anything specific would prevent it. But she admitted didn't have any more info for me.
I've heard of a few MtF individuals online who have induced lactation. I'm currently attempting myself, but I was forced to take a break this past week, and I haven't managed to produce liquid yet. I am taking Fenugreek and Blessed Thistle, and haven't noticed any notable side effects.
I do stress reading up online from as many sources as you can before you put anything into your body. It's important to keep track of side effects and interactions, and even a seemingly informed person can have things incorrect.