I think they may have sugar in them? So I'm not actually sure. Then again you are allowed Muller Light. ... Compare the nutritional information on both : if they're similar; and there's no actual sugars in the ingredients list of the Probiotics, then go for it. Doesn't sound like a bad idea.
Personally I still haven't touched them even though I'm not on RTM or any kind of diet anymore. ... Maybe I'll buy some today and see?