How does a 3-phase meter handle using on 220 volt single phase and does the meter measure the wattage usage accurately?

If you mean 220 single phase as in two hots and a neutral 110V-0-110V (in the US this would be 240V 120V-0-120V), then the answer is most 3-phase meters cannot be used. A few meters can be setup for either configuration, check the manual for the specific one you want to use. If you mean 220V single phase with just one hot wire and a neutral, then a larger percentage of 3-phase meters can be used, and will meter accurately. But again, the meter has have this as one of the setup choices. Check the manual. One possibility would be if you have a meter that can be setup to use 3 CT's and tell it that it is hooked to a wye system with neutral. If it sees current on just one phase to neutral, this is a valid condition, since the system could be feeding unbalanced loads (remember the meter thinks this is a 3-phase system). This would only work if the meters wiring diagram calls for CT's on all 3 phases. Many meters call for only two CT's, calculating the 3rd leg by using the two known values. This type of setup would not meter accurately for your single phase, I believe. And this will not work on a 110V-0-110V system, because a 3-phase meter expects 120 degrees between phases, not 180. Oh, I didn't mention the case where you might have two hots and no neutral. The 3-phase meter would have to be set up for a delta connection as far as the meter was concerned, since there is no neutral. It could work, not sure on this one.