Bismillahi Al-Rahmani Al-Rahim
When something is a community obligation, it basically means that each individual of the community will be considered disobedient if one or more individuals do not fulfill the needs. While fulfilling the community obligation does remove it as an obligation on the others, it does not mean that they should not still do it.
In the case of the question here: Provided the adhan is being made with its proper conditions in on mosque it ceases being obligatory on the others but remains a sunnah to do so.
We should keep in mind that minimalist fiqh (doing only that which is obligatory and leaving only that which is outright unlawful) is, quite literally, playing with fire. Belittling the sunnah is hardly a trivial matter. The predominant position of the scholars of jurisprudence is that fard/wajib and sunnah are the same in that they are all commanded to be done; where they differ is one is punishable for neglecting the former. The same goes for haram and makruh: they both must be avoided, though on is punishable for doing the former.
And Allah knows best.
Wa al-salamu `alaykum,