Best way to approach a partner business to understand the need for B2B web-services

Question

We currently work with a company that has a fairly simplistic web system for processing warranty information. The only way to get data out of it is through excel exporting. Compilation of this data and correlation with our systems has to be manual and makes us be reactive in our response.

The ideal situation would be setting up a web service on their side and automatically mash it up with our data so that we can have good and timely information without human overhead or the weekly bottleneck.

However, when we mentioned this same argument to them, their IT department creeped out from us wanting to access their systems "directly", since they have other information for other vendors which are our competition. In other words, they seem to think it is something weird and insecure.

My question is: how would you make them understand the need to modernize their systems?, have you had any experience convincing the company you want the web-service from?, and, would you go convince them yourselves as a company with the need, or hire a consultant to assess this and speak with them instead?

Edit: We supply custom made electronic devices for our clients which then sell it to end users. End users deal with our clients and, depending on the case, then the client deals with us if they require software/hardware fixes for the next revision.