Infrastructure assets can be stable, long-term investments, and as a result, private equity firms are certainly interested.

In fact, TPG has joined Global Infrastructure Partners – a joint venture of Credit Suisse and GE Infrastructure (NYSE: GE) – to make a preliminary $6.5 billion bid (when you include the debt load) for Asciano, a port and rails infrastructure firm based in Australia.

Actually, TPG has had a mixed performance with Australian deals. For example, the firm was unable to pull off its $11.1 billion buyout of Qantas.

Yet, now the markets are much different, and infrastructure operations definitely need cash – which is tough to get in the current credit crunch.

Asciano has about 8,000 employees and generates $2.5 billion in revenues. Some of its key assets include bulk export facilities, four leading container terminals, Stevedoring equipment and rail operations for freight and commodities. There are also joint ventures, such as Patrick Autocare (processing, storage and distribution of motor vehicles).

Of course, Ascaino has already rejected the buyout offer, but it's going to be tough to get a much higher bid, especially in light of the company's heavy debt load and weak operational performance over the past year.

Tom Taulli is the author of various books, including The Complete M&A Handbook and The Edgar Online Guide to Decoding Financial Statements. He also operates MergerBook.com.