As the U.S. smartphone market nears the saturation point, carriers are increasingly having to choose between growing their subscriber bases and maximizing revenues. But as the operators prepare to release quarterly earnings in the coming weeks, T-Mobile (NYSE:TMUS) still appears to be doing both.

That's the opinion of analysts at Evercore ISI, which published pre-earnings research notes on the four tier-one carriers this week. Citing preliminary quarterly figures released by T-Mobile last week, Evercore said it expects T-Mobile's momentum to continue during the fourth quarter of 2015 both in terms of subscriber growth and EBITDA (earnings before interest, taxes, depreciation, and amortization).

The nation's third-largest carrier posted net adds of 4.5 million during the period, outpacing estimates of 3.8 million to 4.2 million, Evercore noted. "And, while strong customer adds usually pressures EBITDA (given acquisitions costs), (T-Mobile management) recently signaled FY15 EBITDA results would land in the top-half of guidance ($6.8-7.2B, which excludes the impact of leasing and Data Stash). Finally, although the ramping of handset leasing will impact the comparability of results, we expect further progress on levered FCF (free cash flow) following the positive inflection in 3Q."

Verizon (NYSE: VZ) and AT&T (NYSE: T), meanwhile, are largely opting to target more lucrative customers in an effort to maximize profits. That strategy is likely to boost margins, Evercore noted, but could weaken subscriber growth. The analysts predicted AT&T lost 300,000 postpaid phone customers during the quarter; Verizon is expected to post postpaid phone net adds of 525,000, a 21.9 percent increase over the previous year.

And while the analysts expect Sprint's (NYSE: S) aggressive marketing tactics to continue to grow its subscriber base, they question how that effort will impact on the operator's profitability. Sprint's recent embrace of leasing handsets rather than subsidizing them will help its bottom line, Evercore said, but the company may have trouble financing its ambitious transition to small cells.

"On the subscriber side, S is focused on growth (which is most likely detrimental to profitability), and we expect: (1) a second consecutive quarter of postpaid net adds… and (2) postpaid phone net adds…. However, we see the company struggling to generate free cash flow (despite cost cutting measures), which could (a) impact network improvement goals and (b) make S increasingly reliant on alternative financing (e.g., Mobile Leasing Solutions). Net/net, despite improving subs momentum, negative normalized EBITDA growth and FCF questions keep us on the sidelines."

For more:

- check out our wireless earnings calendar here

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