one8ung, I completely agree.
In professional audio by now, there's only one standard powering system any more ("phantom"); it's defined for 48V and for 12V. A microphone can support either one or both. If a preamp or recorder says it has one or both built in, but it fails to work with a microphone that conforms to the standard, then the preamp or recorder maker gets a bad reputation, so they try to avoid that.
That's exactly how standards are supposed to work. Expectations for reliable "interoperation" of equipment from different manufacturers are high, though the equipment prices are correspondingly high as well. You're basically paying for the negative experiences that you _don't_ have to go through, that could cost you your job, since so many professional sound recordists are freelancers. In the professional realm, conformance to standards--playing well with others--is part of how a brand's reputation is established.
In the consumer world there are standards, too, but a whole lot of improvising and adapting and freelancing also goes on. Not just around the margins; some major consumer brands assert themselves by "setting standards of their own" as a conscious marketing strategy.
"Plug-in powering" for electret microphones is a huge example of this. About a year ago I bought a Sony lavalier mike (electret with plug-in powering) but found that it wouldn't work with another piece of equipment that also said it had plug-in powering (same voltage range). I returned the mike, and the store took it back without question; the problem wasn't new to them. Plug-in powering from brand "A" doesn't necessarily equal plug-in powering from brand "B" or even from another division of brand "A"--not even for the same voltage range; the plugs and sockets can be wired in conflicting ways.
Given how critical microphones are to recording, and how critical powering is to microphones, yes, definitely ask as many questions as you have--ask them twice, if that's what it takes to get answers you can rely on.