The benchmark S&P/NZX 50 rose 0.51% to 12,754.59 points on Wednesday, with over 24.5 million shares changing hands worth $106.6m.
Over $26m of the value traded was in Infratil, which ended the day up 3.51% at $11.20.
Overnight, S&P Dow Jones announced that it would add the infrastructure investor to its S&P/ASX 200 index, effective July 23, replacing gold company Spartan Resources.
Matt Goodson, the managing director of Salt Funds Management, pointed out that the stock was trading up 7% earlier in the day.
"It's not so much a surprise that it's been added, but the timing is," Goodson said.
The 50
Across the main board, excluding funds, gainers outnumbered decliners by 43 to 38.
Spark NZ continued its steady recovery, rising 1.93% to $2.64.
In March, the telco traded below $2, a month after it reported a 78% fall in net profit for the first half of the financial year.
Goodson said there was no clear source of Spark's improved share price performance.
"You have to go back three or four weeks now for very vague Australian media pre-speculation that private equity might've had takeover interest in it. There hasn't been any noise around that since then."
Mercury Energy shares lost 1.05% to $6.12 after it gave the market a quarterly operational update, which Goodson said was "pretty solid".
"All the wailing and gnashing of teeth about wholesale electricity prices is going to have to be put on hold for another winter, I think."
Forsyth Barr analysts Andy Bowley and Hugh Lockwood released an investor note on Wednesday in which they lifted their net profit expectations for Port of Tauranga by 3% because of a “favourable pricing backdrop”.
In a separate note, analysts at Forsyth Barr initiated full coverage of Tower with an outperform rating and a 12-month price target of $2.
Port of Tauranga fell 0.7% to $7.05 while Tower gained 2.48% to $1.65.
Small caps
Property management firm Asset Plus lifted 5.13% to 20.5c on low volumes after it told the market it secured a new long-term lease at its 6-8 Munroe Lane development.
It signed a 10-year agreement with a tenant to occupy approximately 1,400 square metres of Level 6. The agreement lifts the property's committed occupancy from 65% to 74%.
Late in the day, NZ Windfarms announced it received final approval from the High Court for its scheme of arrangement with Meridian Energy, paving the way for Meridian to acquire the remaining shares it does not already own.
Meridian ended the day down 0.52% at $5.77 while NZ Windfarms lifted 2.04% to 25c.
"We're about to lose another company from the exchange," Goodson said.