For the sake of daftness, I'm going to show how to do this. I'm going to take the 2nd example of BroadcastService, about In Our Time and give a microformats2 markup for the arbitrary schema vocab.
Immediately, there is some confusion as the various examples given don't match (the JSON-LD is missing all of the episode name information, and has misparsed the dates as text; the microdata and RDFa have injected lots of extra div's that will relayout the page) but I'll see if I can match the microdata/RDFa examples:
<aproperty="url"href="http://www.bbc.co.uk/radio4"><spanproperty="name">BBC Radio 4</span></a>
</div> at
<spanproperty="startDate"
content="2013-11-07T09:00:00+01:00">09:00, 7th of November 2013</span>
</div>,
available online from
<divproperty="publication"typeof="OnDemandEvent">
<spanproperty="startDate"
content="2013-11-07T09:45:00+01:00">09:45 on the same day</span>.
</div>
</div>
</div>
<scripttype="application/ld+json">
{
"@context":"http://schema.org",
"@type":"RadioSeries",
"episode":{
"@type":"RadioEpisode",
"position":"604",
"publication":[
{
"@type":"BroadcastEvent",
"publishedOn":{
"@type":"BroadcastService",
"url":"http://www.bbc.co.uk/radio4"
},
"startDate":"09:00, 7th of November 2013"
},
{
"@type":"OnDemandEvent",
"startDate":"09:45 on the same day"
}
],
"url":"http://www.bbc.co.uk/programmes/b03ggc19"
},
"url":"http://www.bbc.co.uk/programmes/b006qykl"
}
</script>
Things to note here:
I've prefixed the schema-specific properties as a vendor vocabulary ie h-schema-RadioSeries rather then h-RadioSeries to show it's an extension that hasn't been through the microformats process
The Microformats JSON is parsed directly from the HTML, and will be consistent across parsers in differentlanguages. Whereas the JSON-LD is a separate DRY violating piece of data that goes out of sync with the information in the page (as the example from schema.org shows - not sure if that is a parsing failure or poor manual updating)
The jf2 version of the parsed microformats is more compact than the direct version by embedding single-valued properties directly, not as a list - this is derived from the microformats version, and is close to what a correct JSON-LD form would be.
The Microformats markup is more compact than either Microdata or RDFa because of the implied url and name properties.
Nesting other types inside a property is much more compact than microdata and simpler than RDFa