>>16722524 (OP)You don't. As an EE who does systems/signal processing, I'm always amazed when I see economists borrowing our concepts for their time series analysis. Constant velocity models and interacting multiple models make sense when you're talking about local motion of a distant target like an airplane or a submarine or something. They make a lot less sense when you're using a Kalman filter or a Bayesian Gaussian mixture filter to do economic predictions.
I think they just do fairly basic maximum-likelihood and Bayesian estimation strategies and then hope that whatever they are interested into roughly maps onto the concepts from statistics and estimation theory they are borrowing.