Relay-based Railway Interlocking Systems (RIS) control railway components like signals and turnouts safely but are still analysed manually through their relay diagrams, a process prone to errors. Previous works proposed formal methods and industrial tools for RIS analysis, but digitalizing and automatically transforming these diagrams into formal specifications remained challenging. This paper presents a proof of concept using an existing Multimodal Language Model to analyse relay diagrams and automatically generate formal specifications in propositional logic. Our method adopts a prompt-based methodology to guide the expected outcome (model in propositional logic) which is then applied to new diagrams. The results confirm that automatic formalization is feasible and accessible. This work opens promising perspectives for further improving correctness through dedicated prompt engineering or fine-tuning, advancing automation of the formal verification of relay-based railway systems.