It'd be spoilers to fully answer that, but... (spoilers up through where we are now in NA... so Tunguska)
At first Chaldea is indeed restricted to just that tank - for LB1 and LB2, IIRC. Around the time of LB3 they find another base from one of the more enigmatic branches of the Mage's Association that kind of dodged the bleaching by being in a pocket dimension or something and move in there. But later after Tunguska (so post-LB6) they lose that one too, but we've massively upgraded our ride in the meantime - we've got like an airship that can launch the tank if they want to provide air support or something.
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Formerly known as xp1337.
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