GPRS or Edge Howto?

Ok, well you can test in a controlled manner using the Loopback like this:

var at = require("AT").connect(LoopbackA);
at.registerLine('1, CLOSED', function() {
  console.log("I got called");
});
at.debug();

LoopbackB.write("\r\n1, CLOSED\r\n");

Now that actually works, so I think you have some other problem there.

However the following doesn't:

var at = require("AT").connect(LoopbackA);
at.register("> ", function(x) {
  console.log("HANDLER: "+JSON.stringify(x));
  return "";
});
at.debug();

LoopbackB.write("\r");
setTimeout(function() {
  LoopbackB.write("\n> ");
},100);

That was an issue with the AT module, which I've just updated and fixed.

But your other issue ("\r\n>" then " ") was actually the same as the one that was stopping ">" from working a week ago. It should be fixed if you're using an up to date build from GitHub (I fixed it last week), but I guess yours might be older?

If you want to fix it on the existing firmware, you just need to register a handler for ">" without the space. Then you handle the check for the space yourself:

var at = require("AT").connect(LoopbackA);
at.register(">", function(x) {
  if (x.substr(0,2)=="> ") {
    console.log("HANDLER: "+JSON.stringify(x));
    return "";
  } else return x;
});
at.debug();

LoopbackB.write("\r\n>");
setTimeout(function() {
  LoopbackB.write(" ");
},100);