This is certainly possible and does happen.

I remember one leading greyhound trainer who used to enter his hounds as emergencies, knowing the field was full.
On raceday it is alleged he would pay the trainer of the box one dog to scratch it.

Therefore his dog would get box 1.

If you looked at the statistics, it was obvious that this was his modus operandi.

No names mentioned here, but he has now cut right back on doing this, after being investigated.
It does still happen.

The same scenario at the trots, use one horse to take on the odd-on favourite leader and use your good horse to sit just off the pace with cover.

That is why often the second string runner will upset the stable favourite at good odds.