A methodology is proposed for the fast assessment of the impact of electromagnetic loading by surrounding wiring on the signal transmission properties of a high-speed interconnect channel. The proposed methodology is aimed at alleviating the computational complexity of the electromagnetic modeling of the channel including the details of the wiring in its surrounding that, more often than not and especially in the early stages of design, are not well defined and thus are best accounted for through a Monte Carlo analysis. Instead, use of a stochastic macromodel for the channel is proposed that incorporates the electromagnetic attributes of the surrounding wiring through a statistical description of its loading on the interconnects of the channel. The proposed method makes use of parametric rational interpolation to develop a frequency-dependent macromodel that is valid over the multi-dimensional space that describes the uncertainty of the neighboring layout topography. Making use of stochastic collocation, the channel macromodel lends itself to fast quantitative analysis of the channel transmission properties and signal degradation in both frequency and time domain. A simple channel example, which allows us to assess the accuracy of the proposed method, is used to demonstrate the key attributes of the proposed method and comment on its usefulness as a computer-aided tool for noise-aware wiring layout planning.