I find the winter baselayer very warm, so wouldn't be wearing it until temperatures were down to 2 or 3°C. You might feel the cold more than me though, I'm still wearing summer baselayers!
yesterday first little ride with the winter baselayer.
Winterbaselayer + LS Jersey > 10° perfectly fine. With a thermal bib instead of classic one perhaps a few ° less possible, will try this when its getting colder again
I find the winter baselayer very warm, so wouldn't be wearing it until temperatures were down to 2 or 3°C. You might feel the cold more than me though, I'm still wearing summer baselayers!