Integrated Control Systems (ICSs) are often large-scale and highly configurable software-intensive systems-of-systems, with software and hardware components integrated to control and monitor physical devices and processes (e.g., oil and gas production platforms). Employing Product Line Engineering (PLE) is believed to bring potential benefits with respect to reduced cost, higher productivity, higher quality, and faster time-to-market. However, relatively few industrial field studies are reported regarding the application of PLE to develop large-scale systems, and more specifically ICSs. In this paper, we report about our experiences and insights gained from investigating the application of model-based PLE at FMC Technologies, a company developing subsea production systems (typical ICSs) to manage the exploitation of oil and gas production fields. We first discuss the benefits and challenges of applying systematic domain analysis-the first major step of PLE, report on the key domain analysis results and then assess the benefits and challenges of employing model-based PLE at FMC, as a means to improve the quality of their products and the productivity of their product development process.