We extend an existing probabilistic congestion model to consider shielding for crosstalk reduction. We then develop a multilevel router to study the impact of various congestion models on routing congestion by using large industrial design examples. We show that (1) when shielding is applied as a post-routing optimization for crosstalk reduction, the existing probabilistic model, when compared to a deterministic routing-order dependent congestion model, reduces routing congestion by 17.1% on average under the given routing area constraints, or reduces routing area by 9.4% on average under the given routing congestion constraints; (2) our extended probabilistic congestion model considering shielding enables shielding reservation and minimization for routing and achieves routing congestion (or area) reduction by