Military control and railway movement

[imperium3]

I know you need at least 25% MC to be able to rail into a province.

What I am trying to understand is the ins and outs of this.

If I have a unit in a province with, say, 10% MC, it will of course increase the MC. But when is this calculated? Is it an hourly/daily increase or once per turn?

Assuming it is daily - if a unit (with rail movement enabled) is marching into a province when the MC increases above 25%, will it flip to rail movement and arrive very quickly?

How about if the unit is railing in from several provinces away (i.e. it has not started to move into the province in question until MC has already increased above 25%). Will it arrive by rail, or is it stuck with the MC value when the turn was submitted?

[Ace]

MC at the trn begining is relevant.