Can players and coaches be held criminally liable for actions that they take beyond the scope of their game?
Yes. For example, Todd Bertuzzi was convicted with assault causing bodily harm for punching Steve Moore. Since that event happened in British Columbia, it was a British Columbia court that had jurisdiction.
In 2000, Marty McSorley was found guilty of assault for slashing another player in the head with his stick. This also happened in British Columbia: R. v. McSorley, 2000 BCPC 116. The judge quoted an older case, saying:
Patently, when one engages in a hockey game, one accepts that some assaults, which would otherwise be criminal, will occur and consents to such assaults. It is equally patent, however, that to engage in a game of hockey is not to enter a forum to which the criminal law does not extend. To hold otherwise would be to create the hockey arena a sanctuary for unbridled violence to which the law of Parliament and the Queen's justice could not apply.
The judge recognized that there is an "unwritten code of conduct agreed to by the players and officials" including norms of fighting, but that McSorley's actions were outside of those norms. Even a slash directed at the upper shoulder area was too risky (that it might miss, and instead hit the head) to be covered under any consent.
A rugby player was convicted of manslaughter when he aimed to "Pile drive [an opponent] hardest I could into ground" and ended up causing his death: R. v. C.(C.), 2009 ONCJ 249. The judge noted that consent will be implied "with respect to force that is outside the rules but within the scope of the accepted standards by which the game is played." He also found that "[t]he defendant intentionally applied force that was outside the rules of the game or any standard by which the game is played. [The deceased] did not explicitly consent to that force and I am satisfied beyond any doubt that no such consent can be implied."
The issue will be what degree of contact and force was consented to. The factors often cited come from R. v. Cey, 1989 SKCA:
the game of hockey involves a continuous series of assaults. Obviously, most of the body contact is consented to merely by the decision to participate in the sport. To determine at what point this consent disappears is not an easy task, but it must be identified in order to determine when a player moves from conduct calling for the imposition of a penalty into conduct which involves a criminal assault calling for a criminal conviction and sentence
The conditions under which the game in question is played, the nature of the act which forms the subject-matter of the charge, the extent of the force employed, the degree of risk of injury, and the probabilities of serious harm are, of course, all matters of fact to be determined with reference to the whole of the circumstances. In large part, they form the ingredients which ought to be looked to in determining whether in all of the circumstances the ambit of the consent at issue in any given case was exceeded.
Bountygate seems trickier
The rest of this is opinion and is less well researched. I do not believe the above theory of liability (assault vitiating implied consent) is easily applicable to the circumstances of of Bountygate. First, I am not sure this theory of assault is applied in the United States. Second, it seems to me that there would be near insurmountable evidentiary hurdles in establishing that any particular tackle was motivated by an intent to injure (normally, ulterior intent is irrelevant for assault, but it seems to be a factor in considering whether implied consent has been vitiated in the sports context).
However, there may be some kind of conspiracy-based offence available. Given that the offence would have happened entirely in the United States, it would be state or U.S. federal law that would apply and I will need to leave it to another answer to fill in the details of this theory, if it would indeed be viable.