Quick question - are RATP Mobilis tickets valid on TER services within zones (to Rambouillet for instance)? I'm going to presume the answer is no but thought I'd check.
As long as you are in Ile de France region ticketing area you should eb able to use Mobilis.
A good way to use it is to stay further out of Paris - cheaper and nicer often than some Paris accomodation options.
Back in 2006 I stayed out at Rambouillet for a 'Paris' weekend rather than pay Paris hotel prices. Worked well, and in those days we were able to enjoy both Z5300 and BB9200 hauled corails on Montparnasse - Rambouillet!
There's a few BB7200 diagrams that stop at Melun out of Gare de Lyon as well on which the zonal tickets are valid; there use the very comfortable TER refurbished Corail stock. From memory I think there's four diagrams in the day; they use the same xx.19 / xx.49 paths in and out of Gare de Lyon as the regular fast EMU service - they can be identified in the timetable because they go further out than the rest of the services... I forget the exact destination at the moment!
Trains are Paris Gare de Lyon - Laroche Migennes, operated by TER Bourgogne.
About 35 minutes out to Bois-le-Roi, where you have a ~10 connection for a LM - Paris loco-hauled back would be my suggestion of a move.
Errr... I thought the Gare de Lyon workings were non stop at Bois le Roi anyway and you had to get a one per hour from Melun to there and ditto in reverse on the way back? Although that should yield a couple of Z5300s - if you don't get stuck at the level crossing at Bois...
I don't think you're thinking of the right place.
Bois-le-Roi has no foot crossing; there is a subway around halfway down the platform towards LM, towards the back of the train on the side towards Paris.
Thanks for the suggestions all. One last question - does anyone know if the Melun - Montereau via Héricy shuttle is Z5300s at weekends too or only weekdays/peaks? Next time I go I've only got the one weekday evening and I want to use it to track down MS61s as they're getting very thin on the ground these days.
The noises echoing off the tunnel walls are worth recording for posterity. Try this bit off peak then you'll be pretty much guaranteed a fast run for maximum motor noises.