According to https://github.com/dave-p/TVH-API-docs/wiki/mpegts#mpegtsnetworkscan the api/mpegts/network/scan function must be supplied with the uuid of the network, it will then trigger a scan across the muxes contained in that network using whatever tuners are available.
I just tried it (on UK Freesat 28.2E) and it works on my system. Strangely it scans the muxes in the reverse order to normal; instead of H then V and frequency low to high it scans V then H and high to low.
A scan of a single mux can be triggered from the UI by setting its "Scan Status" to "Active". I don't think there is a specific API to do this.
