It seems unlikely that Lens could take the title from PSG (at least the bookmakers think it's unlikely), but if you look at the facts, you'll see: 22 games have passed and Lens is leading. There are only 12 games left, and PSG will be spending their energy in the Champions League, while Lens can focus on Ligue 1 (ignoring the French Cup). At the moment, I would rate Lens's chances of winning the title at 20%, bookmakers estimate its chances at half that.
Lens only focus for French Cup and Ligue 1 match its advantage if want to keep leading top standings in domestic league than PSG have to play at Champion League exactly for this week will face AS Monaco at the playoff round match.
I think has 12 matches left in Ligue 1 and leading first standings behind 1 point remaining with PSG has bigger chance to get domestic league trophy this season, most important Lens will face PSG at games week 29 and playing at their home just need one points enough keep securing first position but 11 matches left have to win.
Winning ratio for Ligue 1 tittle around 20% I think normally for right now has 12 matches left, during few matches left later if Lens keep leading the top position I think easily get raise up until 50% for Lens ration for winning Ligue 1 tittle.