[icegreentea]

I think that the effectiveness of the strategy will depend on the specific plant's pollination/seed dispersal mechanism. And it gets really weird when you consider that you can have plants that over multiple seedling generations (years really) that have a mix of clonal colonies and sexually reproduced offspring dispersed around them.

To the original question, one obvious difficulty is considering how a mechanism encoding directionality in a chemical signal can evolve. It's certainly possible that these fungal networks are weakly directional, and it's also possible for a plant to evolve some sort of gradient sensing mechanism if its root network is sufficiently wide, but it -seems- unlikely. I would totally love to see if we can find an example of it though - it would be sooo cool.