MPLS stands for Multi Protocol Label Switching. It’s technology originally crafted for the Service Provider. It provides a lot of efficiency and flexibility, which is the reason why it’s widely used in the Service Provider networks. Nowadays MPLS is also being deployed in Enterprise and even small networks.
To answer your question:
Yes, your RouterOS powered router supports MPLS, the support has been there for years. And no, if you’re using an SHDSL modem, this does not mean that you’re using MPLS. You’re from the customer edge of the network, so even if your provider is using MPLS in its core network, this happens to you transparently.