The two former Nottingham Forest favourites hugged one another at the final whistle and will meet again on Wednesday week.
City looked to have snatched the winner with a 76th-minute penalty before MacLean powered in the equaliser two minutes later.
In-form Wednesday, whose impressive run has taken them to the fringe of the Championship play-offs, started in confident fashion, full-back Tommy Spur breaking on the left flank but, with time to spare, he ballooned the ball high over the bar from 25 yards.
Midfielder Glenn Whelan, who started his career at City, carved out an ever better opportunity minutes later with a neat interception before picking out the unmarked Chris Brunt who was left red-faced as he miskicked from the edge of the box.
City, who reached the quarter-finals last season, and badly missing the suspended Joey Barton, were soon in trouble again. Kenny Lunt steamed forward to try his luck with a low 30-yard strike, but his effort was smothered on the line by Sheffield-born keeper Nicky Weaver, who had a loan spell at Hillsborough last season.
Micah Richards was lucky to escape a red card after he tangled with Whelan before grabbing him round the neck and pulling him to the ground.
City had an escape on 46 minutes when Sylvain Distin tried to cut out a Frank Simek cross, but only contrived to slice the ball viciously towards his own goal as Weaver pulled off a fingertip save to push the effort over the top.
Brunt's teasing corner was met by skipper Lee Bullen at the far post but his fierce header was cleared off the line by Georgios Samaras.
City, on the back foot for most of the game, then caught Wednesday on the break. Darius Vassell steamed forward and, with the Owls defence looking for offside, he slammed in a low strike which produced a one-handed stop from Mark Crossley.
Distin connected with a Richard Dunne header but powered the ball over the top, before Brunt slammed a stinging drive into the side-netting as the game hotted up.
Weaver kept out a long-range Whelan strike before Wednesday were caught out again on 65 minutes. Vassell beat the offside trap after being played on by Simek, only to be stopped by Crossley who dived at the striker's feet to snatch the ball.
Crossley kept out Samaras' strike before Weaver pulled off a stunning save to fingertip Brunt's screaming effort over the bar.
City broke the deadlock in the 76th minute after Lunt tripped Richards with a clumsy challenge.
Samaras tucked home the spot-kick with ease before MacLean put Wednesday back on level terms with a stunning angled 20-yard shot.
The ball hit the far post on its way over the line. MacLean had a chance to snatch a winner nine minutes from time but sliced Brunt's pass yards wide of the target.