I forgot to add, our 151 took a strange route home last night. It turned left off Entre Rios and up Venezuela. I am not sure why it did this but it caused quite some confusion. Many of the passengers had their smartphones on GPS mode trying to work out where we were.
Surely it is not that difficult, we were all the time parallel with Rivadavia, the numbers will correspond and we crossed all the streets that terminate there. Still I suppose it was easy for me, we joined Rivadavia at Virray Lineas and then it was right into Salguero, so I had no extra navigation to do.
It is however a mystery why the colectivos divert so often.