Fortifications as logistical delay systems

Could heavy siege artillery breach Martello towers, and what value would the towers retain if it could?

Siege artillery can eventually defeat a fortification, but bringing it forward consumes time, transport, and guns needed elsewhere.

Heavy siege artillery could eventually breach a Martello tower. The tower's value lay in making that specialized artillery, its ammunition, and its transport necessary in the first place. Every defended point slowed the attacker and prevented those guns from being used on another task. A defense did not have to be invulnerable to be useful. The Corsican position that inspired the British design mattered because defeating it took disproportionate time.