Leased line and business trunk are basic enterprise communication infrastructures, which can facilitate reliable, secure and yet cost effective communication methods between office locations. With the expension of mobile industry, scale of the fixed line business has been declining in developed countries. This is a good business opportunity for mobile operators to provide mobile enterprise services to replace the fixed line services. This paper analyzes the opportunities and challenges operators facing in this new field. To maximize the opportunities and to deal with the challenges, mobile network architecture needs to evolve to accommodate business requirements for mobile leased lines and business trunks. A telecommunication network architecture i.e. I-Net, is proposed. Future work for implementing the I-Net architecture is also discussed.