Comms allowing teams to help riders get back on after a crash was much more accepted in the past, but seems to be being clamped down more and more by UCI. Generally, you're only disadvantaged by having a crash in terms of having to ultimately expend more energy to get back to the same race position in the bunch you were in at the time of the crash anyway. I can't think of any times riders crashed on purpose from near the front of the peloton thinking it would gain an advantage. At the speeds those guys were going at the time, even with the tow, you've still got to fight through 50 riders again on your own, just to get to the front which is hardly an advantage, when you were already near the front anyway when you crashed? 7 seconds pull is still offset greatly by the extra energy to get back to where you were. I guess you could argue, it reduced the amount of extra effort required simply slipstreaming the convoy bumper to bumper, but an advantage? I don't think there was advantage to crashing and taking a new bike.