Brief Answer:
There's the hope and the data.

Detailed Answer:
The hope is that with narcotic rotation some people have improvements. But the data strongly imply narcotics are just bad for fibromyalgia (well... good if you want to induce it). There's the theoretical story about what is occurring in fibromyalgia (a dysfunction of one's own wiring on one's own hormonal narcotic regulatory hormones called endorphins) and the stuff we actually DO know. People on narcotics get sensitized to pain. This is very similar to fibromyalgia.

So... as you have alluded to.... the standard fibromyalgia treatment does not include narcotics. But the standard hip replacement short term treatment of pain certainly does.

My bias is to tell you about one particular TOTALLY WRONG mathematical representation of this.
https://www.softchalk.com/lessonchallenge09/lesson/Pharmacology/Introduction_088.html
See the curve. They all look like that .. they are all wrong. They stop at zero effect at the bottom.

The dose response curve for pain, as you know, goes well into the negative range. Here's the principles for the curve
You give more narcotic you get more effect up to a point where it's turned on all its switches and the effect is maximum.
Furthermore, there is a learned conditioned response to seek increasing amounts which are a reward.
But the feel of the reward lessens over time (tolerance) and you can become dependent upon getting a reward (dependence).

Ok.... you can do the same thing (in animals too) with going UP from a negative.
Removing a negative is a reward.
You become dependent on having the feel of the relief of the negative
The feel of how bad the negative is, becomes less over time (you become tolerant to the negative).
You become used to having the negative and it's removal over time.

The exercise is the negative. This is why exercise works in fibromyalgia. It feels so good when you stop it.
Link taking (ONLY SHORT TERM NARCOTICS) to doing unpleasant exercise.
Then, when the pattern is established. Taper off the narcotics.
dampers of nerve twitchiness (methylcarbamol muscle relaxant, lyrica, amitryptiline, etc.) may also be helpful

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Brief Answer:
wow, simple question.

Detailed Answer:
great ! Here's some sources on narcotic dose equivalents.
BUT..... there's some complexities involved. First, the duration/time profile of the drugs cannot be matched. How much for how long is not an exact match. In theory they should both be fairly consistent for about 12 hr because they are long acting formulations. There is some increased effect in the first hour as the drugs hit their peaks and some tail off about the time of the next dose. Mostly this isn't a significant effect. Furthermore, morphine is quite notorious both for increased side effects of nausea/bad feelings and a heavy genetic variation in effectiveness. If you don't have a problem with it by the first dose, forget I mentioned that.
http://en.wikipedia.org/wiki/Equianalgesic
http://emedicine.medscape.com/article/0000-overview
Oxycodone is a bit more potent (30-50%) so... 30 of morphine is 20 of oxycodone. These are the standard doses. 10's of oxycodone versus 15's of morphine.

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