It all comes down to what kind of WAN-connection you get through your ISP. If they give you a L2-connection, then you can use it as an extension of your LAN/MAN, and just use L2/L3 capable devices like the ERS5500-series (and all the other ERS-series switches). If they provide a managed L3 VPN, all L3 features will need to be provided on the providers CE-equipment (router).
One thing you may want to start thinking of, given that your provider has an L2-connection, is to set up a SPB network with VSP4000s at the central and remote site. Then you will be in full control of all aspects, both L2 and L3
Brgds,
Øyvind