The idea that the MA doesn't have multidrive missiles and that the Cataphract is their current answer to MDMs is further backed up by some more quotes and snippets of text.
First, Citizen Commodore Luff (the CO of the People's Navy in Exile that carried out the attack on Torch as a Mesan proxy) remarks:
He had to admit that the Cataphracts in his battlecruisers' magazines were better than anything the People's Navy—or State Security—had ever been able to provide him with. They weren't as good as the multidrive missiles the damned Manties had introduced...but they offered a far greater capability than the PNE had ever before possessed, and they could be launched internally, rather than requiring pods.
Secondly, Benjamin Detweiler himself chimes in from ART:
“The same thought had occurred to me,” Benjamin said grimly. As the commander of the Alignment’s navy, he was only too well aware of what the only navies with operational pod-laying ships-of-the-wall and multidrive missiles could do if they were allied instead of shooting at one another.
However he kind of contradicts himself a bit later when talking about the Andermani:
"Get Gustav out of the Sollies’ line of fire and let him take care of us. It’s not like they’re going to need his pod-layers to kick the SLN’s ass! And we just happen to have left the Andies’ support structure completely intact, haven’t we? That mean’s they’ve got plenty of MDMs, and if Gustav comes after us while staying out of the confrontation with the League, do you really think any of our ‘friends’ in Old Chicago’ll do one damned thing to stop him?"
I don't know if the IAN's pod-layers and MDMs aren't fully operational (I thought they were and Benjamin's comments seem to imply that they are) and that's why Benjamin didn't include them in his list of navies alongside the RMN and the RHN with those capabilities or he doesn't consider them as enough of a threat to really worry about yet. Either way, it definitely seems like only the Manties (with Grayson of course), Havenites, and Andermani have MDMs at this time. Although I'm not certain where our Mayan friends are in their buildup and whether or not the MA knows about that...