The Mesh object in the Particle framework is not supporting BT/BLE (802.15.1) but is dedicated to access the OpenThread environment (6LoWPAN 802.15.4).
BT/BLE support is planned for the next release (1.2.0), but the actual feature set for that initial introduction of high level BT/BLE APIs hasn't been disclosed yet.
However, if you want to dive into the lower levels you already can with a local toolchain and monolithic system/application firmware.