Appart from the PI-to-Matlab Utility, there are several other methods to export PI data to Matlab described here: White Paper - Using PI Data with MATLAB. Most of those methods depend on PI Developer Technologies, so in order to deploy those applications, your clients need a PI System Access License.
By the way, the upcoming release of PI AF will introduce native connectivity to MATLAB enabling users to schedule and run their MATLAB functions fully integrated into their analyses. Maybe with this, it would be useful for you to have your own PI System exchanging data with your clients. There are many features already available and others still to be released that expand the possibilities of data exchange using cloud services.