Nbt is being ignored in custommachinery:item requirements in all versions 0.8+
It works fine in 0.7.6 from my testing

json files:
machine

recipe

The issue was that I accidentally deleted String nbt support, so basically instead of

"nbt": "{sometag:\"somevalue\"}"

you had to do :

"nbt": {
    "sometag": "somevalue"
}

And that json to nbt syntax behave weird sometime so now from CM 0.8.7 I reintroduced String nbt syntax.
Both syntax are supported but the String one should be preferred.
Sorry for the delay, didn't had much time to work on CM this month.