Definitely consult the PLB manufacturer.

You might be able to figure it out yourself by firing up your strobe. If you tune a radio to 406 MHz and don't hear any strobe-related interference, you're probably good to go. Test a GPS receiver with the strobe as well. If a cold start takes the same amount of time with and without the strobe, that would tell you a lot.

I suspect that if you put the strobe on one side of your body and the PLB on the other (for example, opposite shoulders) that both would function properly.