Hmmm, I've just been looking at the G3 system and seen it doesn't supply any phantom power, however when I checked out the blurb for the Sennheiser Mke-2 lav mics it says the following:
"It is supplied with a 1/8 inch (3.5mm) Mini (TRS) Output Jack for use with Evolution G2 series wireless systems. It can be powered directly from the SK 100 G2, SK 300 G2 or SK 500 G2 bodypack transmitters. It can also powered directly using Phantom power with the optional MZA 900 P."
Any idea if this is true, or will I need to get separate phantom power for my lav mics?
While you can use phantom power for lavalier mics, this only applies to mics that are hardwired to XLR. Lavalier mics on wireless packs tend to depend on bias voltage provided by the pack, which is really not the same as phantom power. For more information see here...
So short version, phantom power doesn't really apply in this case if you are talking about a lavalier microphone designed to be used with a wireless bodypack.