Hi, I'm new here at the forum so I thought I'd start off by contributing something myself.
This code will spawn buses at all the bus stops - you may use it in your OnGameModeInit(), for example.
Please let me know here if I've missed a stop or if you'd like to provide better coordinates :-)
One stop is broken (the one I commented out). I'm not sure why, but if I spawn a bus there it falls through the ground and respawns a little to the side. I tried spawning it a bit higher but that didn't work either (it did not fall through the ground if I spawned it from Z>80). When I spawn a bus at the same coords as it respawns, it falls through the ground again.

The reason for this is simple, I use VC:MP as a simple platform for running races around Vice City with friends. The buses are meant to be an obstacle, but they might work for some other scenario.

Anyway, here's the code:

// West island
// Airport
AddStaticVehicle(167,-1432.89, -780.50,14.79, 90,-1,-1);
// Sunshine Autos
AddStaticVehicle(167,-1019.04, -917.79,14.44, 45,-1,-1);
// Little Havana
AddStaticVehicle(167,-1128.27, -593.15,11.56,268,-1,-1);
AddStaticVehicle(167,-1062.27, -340.08,10.86,268,-1,-1);
AddStaticVehicle(167, -996.25, -513.60,10.86,180,-1,-1);
AddStaticVehicle(167, -908.65, -660.12,11.20,269,-1,-1);
AddStaticVehicle(167, -987.71, -545.34,10.86,  0,-1,-1);
// Downtown
AddStaticVehicle(167, -385.70, 1008.29, 9.99,339,-1,-1);
AddStaticVehicle(167, -295.24, 1284.02,11.69,  0,-1,-1);
AddStaticVehicle(167, -478.18, 1343.06,11.69, 92,-1,-1);
AddStaticVehicle(167, -743.93, 1318.62,11.69, 90,-1,-1);
AddStaticVehicle(167, -874.54, 1350.92,11.38,180,-1,-1);
AddStaticVehicle(167, -869.61, 1074.28,11.00,180,-1,-1);
// East island
// Ocean Beach
AddStaticVehicle(167,  160.57,-1328.51,10.37,160,-1,-1);
AddStaticVehicle(167,  -24.71,-1565.69,10.39, 80,-1,-1);
AddStaticVehicle(167,  -22.11,-1307.33,10.39,  0,-1,-1);
AddStaticVehicle(167,  -77.85, -982.86,10.40 10,-1,-1);
AddStaticVehicle(167,  120.90, -807.78,10.40,325,-1,-1);
AddStaticVehicle(167,  183.71, -487.13,10.99,  0,-1,-1);
AddStaticVehicle(167,  319.78,  -81.48,10.92,  0,-1,-1);
// Vice Point
AddStaticVehicle(167,  428.77,  310.86,11.56,  0,-1,-1);
AddStaticVehicle(167,  472.07,  628.51,11.29,  0,-1,-1);
AddStaticVehicle(167,  228.68,  718.88,10.99,300,-1,-1);
AddStaticVehicle(167,  306.51, 1047.87,13.22, 10,-1,-1);
AddStaticVehicle(167,  449.16, 1273.10,17.37,270,-1,-1);
AddStaticVehicle(167,  498.60, 1022.64,18.07,190,-1,-1);
//AddStaticVehicle(167,  527.11,  628.24,11.00,  0,-1,-1); <-- This is the broken one
// Washington Beach
AddStaticVehicle(167,  516.14,  400.53,10.99,160,-1,-1);
AddStaticVehicle(167,  492.93,   -1.52,10.99,200,-1,-1);
AddStaticVehicle(167,  434.09, -454.09,10.11,180,-1,-1);
AddStaticVehicle(167,  216.84,  -972.83,10.37,170,-1,-1);

Edit history:
2010-12-23 13:26 UTC: Simplified the coordinates.