With T3 racing towards its 4pm close today, whipped along to the finishing post by Nick Minchin and his commission agents, the SingTel results should focus attention on the underlying question facing investors: is there profit growth in telcos?

The Optus segment of SingTel’s numbers indicate either that Telstra is fighting back and Trujillo might yet deliver, or that the phone business remains one of competition and technology combining to inevitably erode every player’s fat margins.

Michael Sainsbury in the Oz highlights the squeeze:

Optus finance chief Jeann Low said the company had told the market that Optus’s earnings before interest, tax, depreciation and amortisation (EBITDA) margins had fallen from 28.4% to 26%, due to three factors.

“One, being the increased penetration in mobile caps,” Ms Low said. “Two, being lower mobile termination rates that were mandated by the Australian Competition and Consumer Commission. And the third factor being the lower fixed-line volumes that we were expecting due to mobile substitution for fixed-line services.”

Operational EBITDA was down 3.2% to $485 million.

Optus is claiming increased mobile market share, but it’s coming at the cost of lower margins and lower spend per customer. Telstra’s bet on a better 3G network is that it will deliver better market share and a higher spend.

As we’ve ruminated before, punters won’t really know if the Trujillo plan is working until well into next year – which leaves them in the dark about whether to hit the web or visit a Commonwealth Bank branch for some T3 this afternoon.

Heavens knows the commission agents are pushing it along with suggestions that there might be a last-minute rush – when all else fails, try to promote a fear of missing out. The urgency of the message might make a sceptic think there’s not much danger of the offer being over-subscribed by retail investors. Too many are still holding their T2 shares.

Disclosure: The Pascoe family super fund has signed up for a small T3 dose – but don’t read anything into that.