Unfortunately I do not have experience in electronics, i try it.
It is not impossible, but you'll experience a steep learning curve.
First let's assume my interpretation of the operation of the tachigraph is correct (I sincerely hope so).
Next I assume you know how a 3-phase system works. Otherwise look it up. This is essential for understanding the operation. The 3 phases of AC voltage generate a rotating magnetic field within the tachigraph, thus moving the pointer across teh speed scale and the counter along the odometer scale. Since we're not particularly interested in a very smooth motion of these elements, a square wave instead of a sinusoidal wave should suffice. The mechanical inertia of the moving parts will smooth out the movement.
I interpret the information you supplied for the tachigraph such that the 3-phase signal you need to supply to the tachigraph has the relevant information in the frequency, not the amplitude of the voltage. I take this from the fact that the original signal is generated from the revolutions of the train wheels which will lead to a frequency proportional to speed. Therefore your 3-phase signal should have a fixed amplitude (e.g. 24 V ... 30 V, whatever it takes to get the tachigraph working) but a variable frequency, proportional to speed. The signal(s) should look like this:
You'll have to find out which frequencies are suitable by experimenting. Your arduino program will then have to map the input values from the simulator to the respective output frequencies.
