One of the buses is marked "Linea Express" while the other is marked "Metropolitan Transit System". 
Two buses
There might be more than two buses.
exists e1 p1 x1 x2 x3 x4 x5 x6 x7 x8.(ne_org_system(x6) & (x6 = x8) & ne_org_transit(x8) & (x6 = x7) & ne_org_metropolitan(x7) & n_other(x5) & ne_geo_express(x3) & (x3 = x4) & ne_geo_linea(x4) & n_bus(x2) & exists e2.(Recipient(e2,x6) & Theme(e2,x5) & v_mark(e2)) & while(e1,p1) & Recipient(e1,x3) & Theme(e1,x1) & v_mark(e1) & of(x1,x2) & n_thing(x1) & card_eq_1(x1))
exists x1.(n_bus(x1) & card_eq_2(x1) & a_topic(x1))