Yes milk cap 'cultivation' is possible if you expand your definition of cultivation.
Trials in Spain sugest that inoculated trees , Pinus spp. specifically can yield mushrooms after as few as 3years after planting out.
existing Pines can be inoculated by various methods, the best/easiest way is to place fresh cap under the leaf litter under the dripline of the tree.
another is to soak caps/spores in a pail of water with sugar and a teaspoon of salt (to suppress bacteria for a bit) overnight and water that around the base of suitable host trees (in ground or seedlings in pots/tubes)
I've used stem butts put into pots growing Pinus halepensis and P.pinea.
There is mycelial growth , but no fruits yet 3yrs....just an experiment to see what happens.
the soils here are alkaline by nature and so I wont plant them out as it wouldn't suit L.deliciosus. it prefers acidic clayey soils.
From what I can gather L.sanguifluus is better on alkaline soils, but I'm not aware of it occuring in Aust....still looking though.
When people say that "mycorrhizal mushrooms cant be cultivated", what they're really saying is that
1. they cant be grown without a host,
2. they require more money and research than it's worth for someone to attempt if they want to have a guaranteed financial return.
-truffles are valuable enough for research to have taken off and fairly resonable success can be expected, but you need money and time.
-Matsutake have so for proved too unreliable, but I believe that work is still being done.
3. 'you harvest them wild from the forest' in countries where the 'known choice edible' species occur which is, I guess, another reason for not putting effort into attempts at 'cultivation'
So, dont let that statement put you off.
If you love mushrooms, and dont expect (depend on) financial return from your efforts, then go for it.
Give nature half a chance- give a mycorrhizal host tree spores of a suitable species at the roots,
and you're much more likely to get a good result than with no spores.
I've been hearing for some years now that Boletus edulis occurred in Aust. and last year it was reported from South Australia that some where harvested and sold to a restaurant.
first 'official' reports of it in New Zealand where made around 1999-2000.
I dont know if they've been growing in SA for a long time , and if introduced by accident or deliberately.
How could they have gone unnoticed for so long if they've been there for a long time ,
if introduced as mycelium on the roots of living trees- like how Lactarius deliciousus most likely found its way here.
Thousands of hectares of Pine plantation/forest could be yielding much more than just milkcaps ( in diferent seasons)
if the appropriate species where present.
Boletus spp., Edible Tricholoma spp. and Russula spp., Cantherellus spp.
Give it a go, spread milkcaps to pines that don't have milkcaps, they need their mycorrhizal friends.
so looking forward to my first feed of the season.