I don't care, but I'd rather not see 8+ new pages of chapter E for trains .. I can see it now:
x5.1 train OVR,
x5.11 trains smashing AFVs on the track,
x5.2 Boarding trains,
x5.3 Unloading from trains,
x5.4 motion trains and railway gauge compatability,
x5.4 bypassing trains,
x5.6 derailing trains,
x5.61 derailing trains into a bldg & rubble generation,
x5.7 aircraft spotting trains,
x5.8 AA fire from trains,
x5.8 cc against trains,
x5.81 cc rx fire vs trains,
x5.82 cc non-rx fire vs trains,
x5.83 dc & ft vs trains,
x5.84 moving burning trains & smoke,
x5.85 trains & LOS,
x5.9 switching trains,
x5.10 engineer SAN kia & runaway trains,
x5.11 unhooking the caboose .....
.... blah blah blah .. if it comes to this, rather not have trains, JMO.
Preferably, keep it very simple & over-simplify. Two or three paragraphs SSRs (20 or 25 lines of rules) style would be enough .. then armored trains would be a good idea from my POV.