While the major carriers have been fighting amongst themselves over who can release the most limited “unlimited” smartphone data plan, TPG has been working on getting its mobile network ready for customers later this year. Today, TPG announced that it would offer a monthly plan at $9.99 which includes “unlimited” data.

However, TPG is imposing limits a little differently to the three other major carriers; instead of a monthly amount of data at full speed (as per Telstra and Vodafone), or just crippled speed all month (Optus), TPG will offer a “cap” of 1GB of data per day, and as a sweetener, the first six months of the plan will be free.

Like other carriers, exceed that 1GB of data per day, and you’ll be speed restricted to 1Mbps for the rest of the day. This is a touch slower than the others, which are slowing to 1.5 Mbps, but the catch is that it only applies for the rest of the day.

So, conceivably, get your Netflix binge out of the way in the morning (on your train ride to work, maybe), and then make do with 1Mbps data for the rest of the day. That speed should, it’s noted, be ample for browsing news, email, social media and so on.

TPG’s Executive Chairman, David Teoh said in a statement that:

the TPG team has been working hard constructing our own network and I feel proud and excited to be introducing our very first on-net mobile product offering. We are inviting users to register to experience our coverage and network performance as well as to take advantage of unlimited mobile data for free. This promotion is the first of its kind in Australia and signals a new era of competition in the mobile market and will undoubtedly bring great benefit to Australian consumers.

TPG is describing the launch of the plans as a “trial”, so there’s clearly scope for it to change up speeds, data inclusions and pricing before it goes wider. It’s opened up a site where you can put forward an expression of interest, noting that priority will be given to “existing TPG, iiNet and Internode broadband customers.”

TPG has also detailed where it expects to provide mobile network coverage for its trials, and not surprisingly, it’s concentrated around CBD areas, specifically in Sydney, Melbourne, Brisbane, Adelaide and Canberra.

Unlike the established carriers, TPG’s network will initially be limited to a (relatively small) list of suburbs around major capitals Sydney, Brisbane, Melbourne, Adelaide and Canberra. For example, at Ausdroid’s office in Hornsby, TPG won’t (initially) be offering any service .. so it’s for inner-suburb dwellers only at launch.

How quickly TPG will grow beyond that we simply don’t know, but the company has given its expectation that it’ll grow to 80% population coverage .. but how quickly that happens remains to be seen. However, it takes time to build a carrier network (unlike an MVNO which can pop up and disappear overnight), so we look forward to seeing what TPG can do here.