I’ve never had a problem using a standard XL-200 speaker mike on my XG100P so the audio and PTT should work, but the other features like the channel selector and emergency button will be a “try it and find out” kind of thing. The one feature I’d be very skeptical about would be the channel display.
There‘s a third-party outfit called Enduro which sells a gussied-up speaker mike with some of the bells and whistles of the XG-ESM which they clearly say works with the XG100P, so there‘s a good chance at least some of the extended features of the XG-ESM will work.
If you’re thinking of buying an XG-ESM, I’d definitely try before you buy, especially for what they cost; new they’re around $500, but even on eBay they‘re going for hundreds.