Ownship maintain same speed in this demo only. It does not have to. It does not have to go straight. It can do anything. Well in fact moving straight at constant speed is the only situation when this does not work
It can go in circles. It can use other platform's LOB to limit the solution, there are many many uses. Only the solution is limited to constant speed and bearing. Or let's better say, it finds constant speed and heading which matches the LOBs best.
There can be ANY number of LOBs. Well more than two. Matrix is always 4x4. You only have to sum more data while creating the matrix, so the time of the computation depends in linear way on count of the LOBs, which is great. Most least square method applications results in this time requirements.