The metrics you choose are up to you, your team, and your management.
1. What agenda is driving the need for the metrics?
2. What "value-add" goals are established?
3. What questions to you hope to answer with the metrics?
4. What do you intend to do with the metrics?
5. Who is the audience?
6. What do you hope the audience will gain by studying the metrics?
The only thing "special" about IVR is that lots fewer apps do it, compared to GUI and command-line, so there are fewer options for tools, and you have to do a bit of mental domain-translation when you learn about test techniques (because they'll be discussed in terms of the majority technology).
Just adapt whatever metrics your company is accustomed to.