Help understanding transparency in Deferred Rendering?

I've read that transparency is not done in deferred rendering. If you have your Camera Rendering Path set to deferred, any semi-transparent objects get rendered in a forward pass. You can see in the profiler there are some RenderForwardAlpha calls. I'm wondering what that actually means for the semi-transparent objects. Do the normal pixel-light-count rules apply to them, where a certain number of lights are done per-pixel, then the rest are per-vertex? Does multi-sample anti-aliasing get applied to the forward rendered objects? It appears not.

Sorry if I'm not being clear here. Not being a rendering expert, I don't really know what specifically to ask other than: What are the implications of having semi-transparent objects rendered in a forward pass in an otherwise deferred render?