It´s novelty for me, sounds like the knowlegde of it gives you some insight in word order, collocation, passive verbs etc.    I mean, tough it is not everyday you can see people talking about it, it might help you how to use them and get them in English communication in a natural way.   

   As I play and have played by ear most of time, I would use them in a instinctive way without using grammar.  Nice of you having brough the subject to disscuss here; it´s interesting, however I had not met it before as well.

https://arts-ccr-002.bham.ac.uk/ccr/patgram/ch07.html

What the patterns indicate
When you use an ergative verb, you have a choice between two (or more) patterns. These patterns allow you to talk about the world in very different ways. For example, you can choose to indicate that something just happens, perhaps as a natural occurrence, without indicating that someone or something is responsible for it. Or you can indicate that someone or something is the cause of what happens and so is responsible for it. Compare the examples below. (Unlike the other examples in this book, these and the following examples in this Introduction have been invented to illustrate the differences in meaning between the patterns.)

The vase broke. John broke the vase.
The volume often varies. The technician can vary the volume.
Many factories closed. The government's policies closed many factories.

http://en.wikipedia.org/wiki/Ergative_verb

Unlike a passive verb, a nominalization, an infinitive, or a gerund, which would allow the agent to be deleted but would also allow it to be included, the intransitive version of an ergative verb requires the agent to be deleted:
"The window was broken" or "The window was broken by the burglar."
"[…] to break the window […]" or "[…] for the burglar to break the window […]"

http://www.english-test.net/forum/ftopic14046.html
An ergative verb in English is where the verb doesn't have an agent for a subject but the verb in a way expresses the action itself without having a separate subject

http://learnenglish.britishcouncil.org/en/english-grammar/verbs/reflexive-and-ergative-verbs
Nice site with plenty of features of ergative verbs...