It is important to estimate the contribution of the wind generation plants in the evaluation of system generation adequacy for power generation planning. Australia has recently proposed to utilize the diversity of the wind energy resources in Southeast Australian power grid through existing inter-State interconnections. This paper aims to present a probabilistic adequacy model for the capacity credit estimation of wind generation plants in interconnected power systems. In particular, the proposed adequacy model will be applied to investigate how sharing of wind energy resource diversity can enhance the capacity credit of the wind generation plants. The impact of the inter-tie rating and varying wind penetration on the estimated capacity credit of the shared wind generation plants is also investigated. The capacity credits of the wind generation plants in each State are estimated within the purview of National Electricity Market (NEM) framework of Australia. The results obtained from simulations are presented and discussed.