It is quite likely that Muawiya would have practically acted...
It is quite likely that Muawiya would have practically acted against the peace treaty in any case, yet his open announcement of the same from the pulpit, in the presence of a large assembly of Muslims of Kufa, shows his strong reaction. This reaction became visible when he failed in his main mission. It is a great political victory of Imam Al-Mujtaba (as) that through his words and action he proved the difference between monarchy and caliphate.
That is how Muslim thinkers and the ulama could clearly distinguish monarchy from caliphate and declared Muawiya as a monarch. Had the Imam (as) not succeeded in his mission, the Muslims would not have been able to understand the difference between monarchy and caliphate till Doomsday. It is a tragedy that knowledgeable persons have seldom appreciated this great achievement of Imam Al-Mujtaba (as)!
As far as the utility of the terms and conditions of the Peace Treaty is concerned, it was not restricted to their enforcement only; rather it had a wider implication, which should be looked at from different angles. The first condition of the Treaty was that Muawiya was obliged to act according to the Holy Qur’an and Sunnah. Some researchers think that, like other earlier caliphs, the Imam (as) had only formally put this condition as part of the treaty.
However, we do not consider this analysis as correct as it is evident that although the Imam (as) knew that Muawiya would not act according to the Holy Qur’an and Sunnah yet this way the Imam (as) granted only those actions of Muawiya as legal which were according to the Holy Qur’an and Sunnah. If Muawiya acted against the Holy Qur’an and Sunnah, then the responsibility for those actions could not be placed on Imam Hasan (as) as he had not accepted Muawiya as having full authority.
Moreover, if the Muslim Ummah had awakened and launched a movement under the guidance of the grandson of the Holy Prophet SAW), then Imam Hasan (as) would have been legally justified to boycott the government of Muawiya and lead the movement against him as he was not acting according to the Holy Qur’an and Sunnah and was thus breaching the agreement.
The second condition of the agreement was that Muawiya did not have the right to nominate his heir apparent and after him the reign of the government would be handed back to Hasan bin ‘Ali (as). There is no doubt that Muawiya was all the time scheming to nominate his son Yazeed as his heir apparent.