Sounds unbelievable ! Read On.
The organization has been a .NET shop but now wants to implement the WebSphere Portal. Options - dump the entire .NET Team and hire a fresh set of WP programmers.
Or use the Mainsoft's Java EE for Portal Edition. It provides .NET extensions to WebSphere Portal, allowing you to create and deliver a complete front-end Service Oriented Architecture , with equal access to .NET and Java services.
Using a single sign-on, end users gain a personalized, role-based access to .NET and Java applications with consistent branding and navigation. In addition, business analysts can easily compose enterprise applications using .NET and Java components using WebSphere Portal's Application Templates and JSR 168 compliant Inter-Portlet Communications.
Check out the same here.
Read about one of the early adopters here.