Are the military able to 'escort' an aircraft in this situation, until it eventually comes down?
I can comment how it was supposed to be done in my active time, and its long time ago that I legally can do it. With newer equipment available some details will have changed, but the overall aim most probably does still apply all over the world.
In the area of responsibility crewed and armed jets are on a special alert state to be airborne within 10, 15, 30 may be 60 minutes after the order is given by the responsible control center to intercept and identify an unidentified aircraft. They normally operate in pairs. The initial direction and altitude informations lead the interceptors within the range of the onboard radar system, and with the help of that the jets will maneuver within visual range to identify the type of aircraft, its altitude speed and track. With means of communications including visual signals the crew tries to get the attention of the rouge aircraft. This is done by flying close to the cockpit of the intercepted aircraft, and yes, it can be done also during night. Positioning one fighter in front of the not responding aircraft while waggling the wings is an internationally understood sign to follow that fighter aircraft for a landing. If no reaction from the rouge aircraft is received but it is assumed that the cockpit of the intercepted aircraft is occupied and the signals have been received, the fighter might use some of their hardware to change the mind of the crew of the intercepted aircraft by firing some tracer shots in front of the rouge aircraft. If still no reaction could be observed the next most obvious course of action would be to monitor and report until fuel would necessitate to return to base.
The words from the transport / defence minister "what should we have done, shoot it down?" are ridiculous, because it neglects the primary purpose of air policing (identifying unknown flying objects) and declares the last option of air policing (using weapons when apropriate) as not practical. Even if it was known in an early state that MH370 had turned around and was identified on military primary radar, it would have been apropriate to alert air defence and raise the alert state of the designated jets ( highest state on ground would be with running engines ready for speedy takeoff). Such facts should be in the textbook of an air defence minister and his statements are loughable the least.
If i'm allowed an personal oppinion, I think that the military would have been able to respond in appropriate mannor because that's what they are there for in peace time, but was never ordered to to so or even was ordered not to follow the normally established procedures for such events. When the aircraft disappeared from the primary radars, a scramble of jets had become useless.
Could a possible plan to hijack the aircraft plan on such behaviour? I think so, and the fact that the duties of the air defence and air tranport sections are performed by one minister makes that even more plausible. How would a transport minister, responsible for the safe conduct of civil air travel order any kind of weapon employment against a civil aircraft in his duty as defence minister? Yes, knowing that and knowing the person of the minister (which I do not do) might lead to the assumption that the military would not be involved in an early state of such hijacking.
Not saying that it was one though.