A T-Mobile spokesperson told us in a response to our story earlier that yes the carrier is going to have an iOS device-compatible “4G” HSPA+ Mobile network available to attendees in Moscone. The 3G signal that our reader caught was not a fluke.

While upgrading coverage inside the West side of the Moscone Center, T-Mobile has also deployed 4G HSPA+ service in the 1900 MHz band to test the live network on a small scale. As part of the company’s previously announced $4 billion network modernization effort, T-Mobile plans to launch 4G HSPA+ service in the 1900 MHz band in a large number of markets by the end of the year, which will make our 4G network compatible with a broader range of devices, including the iPhone.

NOTE: The time and location of this test is just coincidental.

For those with unlocked devices, it might be a great time to try T-Mobile’s $30 unlimited data prepaid plans (ahem Virgin).

This is clearly great news for Europeans who carry T-Mobile iOS devices too. It is surely also welcome news for other Moscone exhibitions including Google I/O later this month.

T-Mobile’s CTO in March 2011 said:

A nice side benefit of the refarming effort is that our 4G network will be compatible with a broader range of devices, including the iPhone. The other important benefit of our network modernization effort is the coverage improvements it will deliver, especially when it comes to in-home coverage. As we refarm our 1900 spectrum, we will continue to fully support our customers with 2G devices.

Even though it often bashes the iPhone in ads, or more specifically the iPhone’s network speed, T-Mobile was happy to talk about Apple’s recent decision to unlock iPhones that are out of contract:

Today we have more than one million unlocked iPhones running on our network. T-Mobile currently offers microSIMs for customers who already have a GSM phone they want to use on the T-Mobile network, including an iPhone. In order to set up an unlocked iPhone on T-Mobile’s network, customers simply need to purchase a microSIM card and select a T-Mobile Value plan that suits their needs.

T-Mobile’s Value plans enable customers who bring their own smartphone, such as the iPhone, to save money. For example, T-Mobile’s Value family plan with unlimited talk, unlimited text and unlimited data with 2 GB of high-speed data is just $49.99 per line for two lines.

In addition, we will continue to deliver more value to customers as we expand and modernize our 4G network. Beginning this year, we will introduce HSPA+ service in our 1900 MHz PCS spectrum. When we do, our 4G network will be compatible with a broader range of devices, including the iPhone.

Virgin announced a $30 prepaid plan today. T-Mobile also offers an unlimited data prepaid plan for $30 a month (which would be faster than Virgin’s if T-Mobile’s “4G” 1900MHz spectrum could apply).