I suppose its extremely nieve to assume that a traction package appears as a purely resistive load then?
Do they fit reactive power sinks/sources to substations or is it simply drawn from/pushed two the grid (some sort of static thing I would assume rather than a synchronous condenser).
Very, but it depends on the age and quality of the system to be honest.
Modern VSDs (Variable Speed Drives) draw an almost perfect pure resistive load, regardless of how inductive the motor is, they also draw very little in the way of harmonics. The main driver for this is a new standards coming in from the National Grid, EU, IET (Institute of Enginering and Technology, formally the IEE), etc. All modern rail vehicles use AC Motors and Variable Speed Drives, so theorectially they are near perfectly resistive with no harmonics, realistically I'd expect a power factor (Amount of active power compared with aparent power) to be around 0.95 for old equipment and 0.99 for newer equipment, since it's very rare anything is perfect, but I have seen some ABB equipment on bench test for a variable load VSD driven induction device running at 0.99995 and that is very impressive (and expensive!).
On older AC systems, not used in the rail industry (at least not extensively) connect directly to the 3phase 50Hz grid, so will ONLY run at 3000, 1500, 750, etc. rpm, and are only really useful when you have all three phases available, not so on rail. These older (and still used for single speed systems) systems have capacitor banks to correct the inductive nature of the motor, but they produce relatively high levels of harmonics, not something you want kicking around as it tends to boil transformers and make power electronics go pop.
Older rail systems tend to use DC traction motors, and indeed before Thyristors where starting to be used (on 87101) very little in the way of power electronics was used, making the use of AC traction motors near impossible as you cannot acheive the switching frequencies needed with Reeds or Relays. Tending to rely on DC traction motors meant that power was 'decided' by chaning the armature or winding currents, usually by altering the voltage across these components via a rectifier.
In such a system the inductive nature of the wound devices (motors, transformers) will transfer to the grid connection, but back then, we either didn't care, or just fitted insanely large electrolytic capacitors with little care for harmonics (electrolytic capacitors are made of aluminium and paper, don't work above 80C (go pop) and have extremely poor harmonics performance. Neither of these are desireable in a modern system, hence moving onto the use of three phase tracton motors fed by variable speed three phase drives (invertors), another advantage being that these can be fed from either AC or DC feeds.
